High Quality Pharmaceutical 8mm Rubber Plug
8mm plunger stopper
Dental cartridges
Siliconized
1.5mL · 3mL
USP / EP compliant
Low friction · factory direct
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Description
CARTRIDGE PLUNGER · SILICONIZED · PHARMACEUTICAL GRADE
8 mm
Pharmaceutical
Rubber Plug
for Cartridges
1.5 mL · 3 mL cartridge · siliconized · low friction · USP/EP
A high-quality 8 mm pharmaceutical rubber plug (plunger stopper) engineered for use with 1.5 mL and 3 mL glass cartridges - dental local anaesthetic cartridges, insulin pen cartridges, and pharmaceutical injection cartridges. Siliconized for low sliding friction, validated for plunger rod engagement, and compliant with USP and EP pharmacopoeial requirements for injectable container closures.
8MM PLUNGER STOPPER
dental cartridges
siliconized
1.5ML · 3ML
USP / EP COMPLIANT
low friction · factory direct
8 mm
plug diameter
1.5 · 3ml
cartridge fit
silicone
siliconized surface
USP/EP
compliant
PRODUCT SPECIFICATIONS
8 mm pharmaceutical rubber plug - complete specification
The 8 mm siliconized rubber plunger stopper is the standard pharmaceutical-grade closure for 1.5 mL and 3 mL glass cartridges used in dental local anaesthetic delivery, insulin pen injection, GLP-1 pen injectors, growth hormone pen systems, and other prefilled cartridge drug delivery devices
| product | 8mm siliconized rubber plug |
| diameter | 8 mm ( plunger OD ) |
| cartridge compatibility | 1.5 mL · 3 mL glass cartridge |
| rubber material | Bromobutyl (BIIR) - standard |
| Surface treatment | Siliconized (silicone oil coating) |
| silicone oil grade | Pharmaceutical-grade PDMS |
| Sliding force | ≤ 20 N (siliconized) |
| Break-loose force | ≤ 25 N |
| Endotoxin limit | ≤ 0.5 EU/plug |
| Packaging | Bag of 1,000 (standard) |
| Sterilisation | Gamma / EO - on request |
| compliance | USP <381> · EP 3.2.9 · ISO 11040 |
| COA | Per lot - included |
8mm plunger plug - the role of the closure
In a glass cartridge drug delivery system, the rubber plunger (also called the back stopper or piston) sits at the non-needle end of the cartridge. When the plunger rod of the pen injector engages the threaded socket on the plug and advances, it pushes the plug forward through the cartridge - displacing the drug through the needle seal and out the needle. The plug must slide smoothly, seal perfectly, and not interact chemically with the drug.
Siliconized surface - why every plug needs it
Without siliconization, rubber-glass friction is high - resulting in jerky, inconsistent drug delivery, inaccurate dose volume per injection cycle, and patient discomfort from unpredictable injection resistance. Pharmaceutical-grade PDMS silicone oil applied at controlled surface density provides a consistent, low-friction boundary layer between the rubber plug and the glass barrel inner surface across the full life of the cartridge.
ISO 11040 & USP/EP compliance
ISO 11040-5 defines the dimensional and performance requirements for rubber plunger stoppers in prefillable glass syringes and cartridges. USP <381> and EP 3.2.9 define the extractables and chemical compatibility requirements. Our plugs are manufactured and tested to all three standards - with the CoA confirming compliance on every lot
The friction performance of a cartridge plug is a critical functional parameter - directly determining dose accuracy, injection force, and patient experience. Our siliconized plugs are tested to the friction parameters defined in ISO 11040-5 and EP 3.2.9.
≤ 20 N
Sliding force
ISO 11040-5 · tested per lot
The sustained sliding force required to move the plug at constant velocity (5 mm/min) through the glass cartridge barrel. Values ≤ 20 N are required by ISO 11040-5 for pen injector cartridge plugs. Our siliconized plugs typically achieve 12–18 N, well within specification.
Typical sliding force: 12–18 N
Measured at 5 mm/min crosshead speed
Tested in standard 1.5/3 mL cartridge barrel
≤ 25 N
Break-loose force
Initial displacement · first movement
The break-loose force is the peak force required at the beginning of plunger movement from a stationary position - typically higher than the sustained sliding force due to static friction. Values ≤ 25 N ensure smooth dose initiation without the "surge" effect that causes inaccurate first-dose delivery.
Break-loose: typically 16–22 N
Low break-loose prevents dose surge
Critical for first-dose accuracy in pen injectors
PDMS
Pharmaceutical-grade silicone oil
Polydimethylsiloxane · pharma grade
Only pharmaceutical-grade polydimethylsiloxane (PDMS) silicone oil is used - not industrial silicone and not silicone emulsions. PDMS at pharmaceutical grade has a documented extractables and leachables profile, is insoluble in aqueous drug formulations, and is accepted by all major regulatory authorities as a component of injectable pharmaceutical containers.
Pharmaceutical-grade PDMS only
Controlled surface density per plug
FDA/EMA accepted injectable contact material
Sliding force comparison - siliconized vs. non-siliconized
| Plug condition | Break-loose force | Sliding force (sustained) | Force consistency | Dose accuracy impact |
|---|---|---|---|---|
| Siliconized (this product) PDMS coat applied |
16–22 N | 12–18 N | CV < 8% | Excellent - uniform dose delivery |
| Non-siliconized (reference) | 35–55 N | 28–45 N | CV 15–25% | Variable - dose surge risk |
| Lightly siliconized | 22–32 N | 18–26 N | CV 10–15% | Acceptable - marginal |
| Over-siliconized (excess oil) | < 10 N | < 8 N | Unpredictable | Poor - stopper migration risk |
Forces measured by tensile testing machine at 5 mm/min crosshead speed in 1.5 mL glass cartridge barrel at 20 °C. CV = coefficient of variation across 10-plug sample.
COMPATIBILITY GUIDE
Which cartridge uses this plug - and how to confirm fit
The 8 mm rubber plug is the standard plunger stopper for the most common pharmaceutical glass cartridge formats globally. Use this guide to confirm the correct plug specification for your cartridge before ordering.
ISO 11040-1 · 8mm bore · dental · veterinary
The 1.5 mL glass cartridge is the dominant format for dental local anaesthetic delivery (lidocaine, articaine, mepivacaine, bupivacaine) and is also used in veterinary pharmaceutical pen systems. The inner bore is dimensioned for an 8 mm plunger plug per ISO 11040-1. Our plug is precision-manufactured to fit the 1.5 mL cartridge inner bore with the correct rib interference for a hermetic seal without excessive friction.
Inner bore: 8.0 mm ± 0.05 mm
Plug provides two full contact rib seals
Plunger rod thread: ISO 11040-5 standard
Compatible with all major dental cartridge brands
1.5 mL / 1.7 mL dental
Lidocaine HCl
Articaine
Mepivacaine
Veterinary
ISO 11040-1 · 8mm bore · insulin · GLP-1 · GH
The 3 mL glass cartridge is the universal format for insulin pen injectors (100 U/mL, 300 U/mL), GLP-1 receptor agonist pens (semaglutide, liraglutide), growth hormone pens, and other injectable pen drug delivery systems. The 3 mL format uses the same 8 mm inner bore as the 1.5 mL cartridge - the same 8 mm plunger plug fits both, with only the cartridge body length differing.
Inner bore: 8.0 mm ± 0.05 mm (same as 1.5 mL)
Standard plunger rod thread engagement depth
Longer stroke required - same plug, longer barrel
Compatible with BD, Gerresheimer, Schott 3 mL cartridges
3 mL insulin pen
GLP-1 pens
Growth hormone
Peptide injectablesF
ertility hormone
Full compatibility reference - cartridge formats & drug type
| products |
 |
 |
 |
 |
 |
| Cartridge format | Volume | Inner bore | 8mm plug fit | Drug application | Pen system examples |
|---|---|---|---|---|---|
| 1.5 mL dental Recommended | 1.5 mL / 1.7 mL | 8.0 mm | ✓ Direct fit | Local anaesthetic (dental / ENT) | Septodont, Dentsply, Carestream, Pierrel |
| 3 mL insulin pen Recommended | 3 mL (300 units) | 8.0 mm | ✓ Direct fit | Insulin 100 U/mL · 300 U/mL | NovoNordisk PenFill®, Lilly, Sanofi |
| 3 mL GLP-1 pen Recommended | 3 mL | 8.0 mm | ✓ Direct fit | Semaglutide, liraglutide, dulaglutide | Ozempic®, Victoza®, Trulicity® pen format |
| 3 mL growth hormone pen | 3 mL | 8.0 mm | ✓ Direct fit | Recombinant somatropin (rhGH) | NordiFlex®, Genotropin GoQuick® pen format |
| 1.5 mL veterinary cartridge | 1.5 mL | 8.0 mm | ✓ Direct fit | Veterinary local anaesthetic | Virbac, Dechra, CEVA veterinary cartridges |
| 3 mL fertility hormone pen | 3 mL | 8.0 mm | ✓ Direct fit | FSH, LH, hCG preparations | Gonal-F® pen, Puregon® pen |
| 2.25 mL autoinjector | 2.25 mL | 9.0 mm | ⚠ Check bore | Subcutaneous biologics (larger bore) | Verify inner bore before ordering |
| 1 mL prefilled syringe | 1 mL | 6.35 mm typical | ✗ Different size | Vaccine, heparin flush, insulin | Use 6.35 mm syringe plunger stopper |
How to confirm compatibility before ordering
Measure the inner bore diameter of your glass cartridge at the filling zone (mid-barrel). If the inner bore is 8.0 mm ± 0.1 mm, this plug is compatible. If you are unsure, send us a sample cartridge and we will perform a plug fit test and provide a written compatibility report. We also supply a plug gauge kit for incoming inspection at your facility.
MATERIAL & QUALITY
Bromobutyl rubber - the right material for cartridges
The rubber compound selection for a cartridge plunger stopper is as critical as the siliconization. Bromobutyl rubber (BIIR) is the material of choice for injectable drug cartridge closures - chosen over standard butyl, nitrile, and natural rubber for its superior chemical resistance and extractables profile.
Why bromobutyl rubber
Bromobutyl rubber (BIIR) contains bromine substitution on the isobutylene-isoprene polymer backbone - giving it significantly lower gas permeability, broader chemical resistance, and a cleaner extractables profile compared to standard butyl or chlorobutyl alternatives.
Low gas permeability
BIIR provides the lowest O₂ and H₂O vapour permeability of any pharmaceutical rubber type - protecting oxygen-sensitive drug formulations (e.g. adrenaline in dental cartridges) from oxidative degradation over the cartridge shelf life.
No nitrosamines - clean cure system
The rubber formulation uses a non-nitrosamine-generating cure system - compliant with current ICH and EMA guidance on nitrosamine impurities in pharmaceutical products. Material safety declaration and formulation information available for regulatory submission support.
Low extractables - USP <381>
Bromobutyl plugs in direct drug contact must pass USP <381> elastomeric closure tests - including non-volatile residue, heavy metal extractables, and biological reactivity. Our plugs are formulated and tested to meet these limits with margin
Low friction.
Precise dose.
Every injection.
Request samples for plug-cartridge compatibility testing, friction force measurement, or extractables data. Send us your cartridge and we will run a plug fit and friction test and provide a written report before you commit to an order.
Plug diameter
1.5 mL · 3 mL cartridge
Sliding force
Siliconized PDMS · ISO 11040-5
Bromobutyl
Low extractables · no nitrosamines
Factory direct
CoA · DMF · compatibility test
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