Rubber Bung Plugs – Custom Conical Stoppers for Labs & Industry
In scientific laboratories, food and beverage processing, home brewing, and chemical storage, maintaining airtight isolation is critical. Standard containers, glass flasks, carboys, and storage barrels rely on a reliable friction-based seal to prevent evaporative loss, oxidation, or contamination. Rubber Bung Plugs (tapered conical stoppers) are engineered to satisfy this demand. By utilizing a tapered geometry, these bungs adjust to varying neck inner diameters, providing a airtight physical seal. Whether you require solid bungs for complete isolation or bored bungs with pre-molded holes for airlocks and tubing, custom molded bungs deliver clean, food-safe, or chemically inert sealing.
At Xiamen Best Seal, we manufacture custom conical rubber bungs and laboratory stoppers in diverse sizing and compound choices. Operating from our ISO & TÜV Certified Facility, we compound premium methyl-vinyl silicone (VMQ) for food and medical grades complying with FDA 21 CFR 177.2600, along with weather-resistant EPDM and solvent-resistant Nitrile (NBR). We support custom molded bore holes (single, double, or multi-hole configurations) to fit glass tubing or fermentation locks. All custom bungs are Quality Managed to IATF 16949 Standards and produced to a Strict AQL 0.25/0.40 Quality Protocol within our UL Certified Facility.
✵ ˚ : · ✬ Technical Features of Our Rubber Bung Plugs ✬ · : ˚ ✶
Why laboratory managers, beverage producers, and chemical engineers specify Xiamen Best Seal's bungs:
🍏 Food & Medical Grade VMQ
Molded using high-purity, platinum-cured VMQ silicone that is free of plasticizers, phthalates, and heavy metals, meeting FDA and LFGB food contact standards.
🔬 Custom Drilled & Molded Holes
Available as solid plugs or bored with single, double, or triple holes, precision-molded to accommodate standard airlocks, glass tubes, or probes.
🧪 Chemical & Solvent Stability
For chemical processing and laboratory uses, our specialized EPDM, NBR, and CR compounds resist dilute acids, alkalis, and cleaning agents.
Rubber Bung Plug Custom Options
Every container neck diameter, depth, and chemical exposure differs. We engineer custom bungs to your exact dimensions:
| Design Parameter | Custom Engineering Option | Engineering & Application Notes |
|---|---|---|
| Elastomeric Compounds | VMQ Silicone (Platinum or Peroxide cured), EPDM, Nitrile (NBR), Neoprene (CR), Natural Rubber | VMQ silicone is standard for sanitary/food contact; EPDM and NBR provide chemical/acid resilience for labs. |
| Sizing Categories | Standard Standardized Stopper Sizes (#000 to #16) | Bespoke conical diameters | Taper angles are designed to secure a tight wedge fit, preventing plugs from sliding out. |
| Bore Hole Configurations | Solid (no hole), 1-Hole, 2-Hole, 3-Hole | Custom bore diameters (2.0mm to 25.0mm) | Bore holes are engineered to grip glass tubing or plastic airlock stems tightly without tearing. |
| Hardness (Durometer) | 35 to 80 Shore A | Softer grades (35-45 A) provide a highly conforming seal on delicate glass containers; firmer grades (60-70 A) resist heavy pressure. |
| Color Matching | Natural translucent (VMQ), solid white, black, grey | Custom Pantone matching | Translucent silicone is ideal for food processing lines to visually verify internal cleanliness. |
| Material Compliance | FDA 21 CFR 177.2600, LFGB, USP Class VI, RoHS, REACH | Ensures no toxic outgassing or pigment transfer in pharmaceutical, food, or brewing applications. |
Strict AQL 0.25/0.40 Quality Standards
Because parting-line flash, surface inclusions, or dimension shifts can cause bungs to slip out or leak air, we verify every production batch. All bungs are verified under our Strict AQL 0.25/0.40 Quality Protocol, using colorimetric and laser sorting machines.
Versatile Application Scenarios for Rubber Bung Plugs
★┊ Engineered for Laboratory, Beverage & Food Isolation
Our custom-molded conical rubber bung plugs provide secure seals, chemical resistance, and airlock support across industries:
- ◌ Laboratory Research & Chemistry: Plugs glass test tubes, flasks, and carboys, sealing corrosive chemicals and preventing acid vapor escapes.
- ◌ Fermentation & Home Brewing: Bored silicone bungs secure airlocks onto beer and wine fermenters, releasing CO2 while keeping airborne yeast out.
- ◌ Industrial Chemical Barrels: Plugs bung openings in metal or plastic storage drums, preventing leaks and moisture ingress during shipping.
- ◌ Sanitary Piping & Food Processing: Seals pipe ports and bypass conduits during Clean-In-Place (CIP) cleaning, maintaining sterile fluid systems.
Bulk Packaging & Custom OEM-Ready Logistics
To support automated packaging lines and maintain clean elastomer surfaces, all rubber bungs are packed in dust-sealed PE bags inside double-walled corrugated cartons.
| Category | Packaging Details |
|---|---|
| Inner Protective Packaging | Sealed thick PE bags labeled with exact nominal sizes, color codes, raw materials, and batch numbers. |
| Outer Shipping Cartons | Double-walled corrugated shipping cartons, reinforced with corner protection and water-resistant wrap. |
| Palletization | Euro or standard pallets wrapped in protective plastic stretch film and secured with high-tension strapping. |
| OEM Logistic Customization: Custom packing counts, kitted sets, and barcode integration directly compatible with your warehouse systems. | |
🚚 Global Trade & Freight Methods
| Method | Details |
|---|---|
| Express Courier | DHL, FedEx, UPS (ideal for pipeline maintenance emergency parts and prototype samples) |
| Bulk Logistics | LCL/FCL ocean freight from Xiamen Port, or air freight cargo for urgent utility schedules |
| Trade Terms | FOB Xiamen Port, EXW, CIF, DDP (delivery directly to your warehouse or project depot) |
Compliance & Quality Management
Best Seal OEM Factory Statement: 1. We are a ISO and TUV certified factory. 2. We are specializing in rubber industry for over 20 years. 3. All our products can be RoHS, REACH, UL, Prop 65, FDA, 3A compliant. 4. Quality Managed to IATF 16949 Standards. 5. Strict AQL 0.25/0.40 Standards for Dimensional Accuracy.
Rubber Bung Plugs FAQ
❓ Why is silicone preferred over natural rubber for brewing and food containers?
Platinum-cured silicone VMQ is chemically inert, odorless, and flavorless, meaning it will not leach chemicals or odors into beer, wine, or food products. It also resists sanitizing chemicals and can be autoclaved or boiled to maintain sterility, whereas natural rubber degrades and leaves black residues after repeated sanitization.
❓ Can you customize the bore hole sizes in the rubber bungs?
Yes. We can design mold cavities to include bore holes of any diameter (e.g. 5mm, 9mm, or 12mm) to guarantee a tight seal around airlocks, sensors, or tubing. This molded-hole process is cleaner and more precise than manual drilling, ensuring there are no internal tearing risks.
❓ Do you manufacture chemically resistant EPDM bungs for industrial solvents?
Yes. We compound industrial-grade EPDM and Nitrile (NBR) bungs specifically for sealing chemical containers, test devices, and storage drums. EPDM offers excellent resistance to polar solvents, steam, and ketones, while NBR is ideal for oil-related environments.
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