Closure Fittings,
and Funnel


Flexible stoppers and caps are the only solution for glass carboys, because glass carboys have irregular necks. However, the flexible materials used to make stoppers and caps can: 1) Harbor contamination; 2) Impart, or carry over, flavors; 3) Deteriorate when treated with washing and sanitizing agents, and 4) Permit the passage of oxygen. BetterBottle PET closures, which fit all sizes of BetterBottle carboys, have none of these drawbacks. The closures are made of an incredibly tough, proprietary PET that does not stain or impart flavors and is easily cleaned and sanitized. Teflon-encapsulated, Viton O-rings create precision seals that require no lubrication. Two models are available: A Universal model with a 1/2" port that has an O-ring seal and two Big Blow models, one with a 3/4" NPT pipe thread and the other with a 15mm BSPT pipe thread.

Utilizing new technology, which accurately measures trace concentrations of oxygen in closed spaces, BetterBottle engineers determined that BetterBottle PET O-Ring Closures are extremely effective at blocking the passage of oxygen. Some types of closures, notably silicone rubber stoppers,are very oxygen permeable and one type of closure is very leaky. Click HERE to view this important study (1.5Mb PDF).

Testing a BetterBottle PET Closure for Oxygen Leakage
Negligible -

Additional Information -
Use the popup menus associated with Closures & Funnel tab at the left side for random access to all the specific information relating to closures. Scrolling down this page will access the same information in sequential fashion.

Chemical Resistance of BetterBottle PET Closures - In general, avoid very strong caustics, such as KOH and NaOH (lyes), and concentrated aliphatic ketones (e.g., essence oils). For additional materials specifications, please refer to the Technical tab at the top of this page.

PET O-Ring Closures

Universal Closure - This PET closure is designed with 1/2" port and comes with a removable plug installed. The port is designed so a 1/2" OD tube can be inserted to blow off foam during primary fermentations. Optional, compatible fittings include: 1/8" NPT threaded plugs, equipped with 90° or "T" hose-barb adapters, and the low-profile BetterBottle DryTrap™ fermentation lock, which requires no liquid. The hose-barb adapters are generally used for connecting 1/4" ID gas purging and pressure balancing hoses. As a rule, the hose-barb fittings are only used during racking, so a given location may require no more than one or two sets. Refer to How-To Tips at the left side of this page for information regarding the use of the hose-barb adapters for low-oxygen and oxygen-free racking. Refer to DryTrap at the left side of this page for details about this exciting alternative to liquid-filled fermentation locks.

Big Blow Closure- This PET closure makes it possible to attach large-diameter, rigid pipe or tubing to BetterBottle carboys for blowing off the thick foams that develop during primary fermentations of some beers and even some wines. Big Blow closures are available with either 3/4" NPT or 15mm BSPP threads. The following threaded or solvent-weld pipe and fittings will make a rigid blow-off tube: a 90° street elbow with a 3/4" NPT or 15mm BSPT male thread; a 6" (15.25 cm) nipple; a 90° elbow; and a 18" (45.75 cm) length of pipe, threaded on one end. Most hardware stores carry rigid PVC pipe that can withstand chlorine-based sanitizers. If you have access to polypropylene pipe, it is a better choice. Alternatively, a threaded 90° hose adapter can be used to connect to PET-lined, flexible tubing (see Tubing at the left of this page).

Use - BetterBottle PET closures are designed so the O-rings seat on steps, rather than in grooves; making the O-rings easy to remove for cleaning or service. The Viton O-ring that creates the seal between the closure and the neck of a BetterBottle carboy is Teflon-encapsulated (not just coated), so the seal will remain slippery without lubrication. Note: Use only BetterBottle O-rings for replacement.

Before inserting a closure into the neck of a carboy, the large O-ring should be pushed all the way onto its step. Before inserting a hose or fitting into the port of the universal-style closure, the small O-ring should be pushed all the way into its seat. Before removing a PET closure from the neck of a carboy, open its port to prevent suction. A sticky pad of the type used for opening jars makes it easy to grip a PET closure for removal. A Blue Handle can also be used to remove a closure with minimum effort.

A sticky pad makes it easy to grip a PET closure               A blue handle can be used to grip a PET closure

Three-part air locks and some other fittings may not seal in the 1/2" port of the universal-style, BetterBottle PET closure without a few turns of Teflon thread tape (available at hardware stores). Military-grade Teflon thread tape is thicker and easier to use than commercial grade, but either type will serve the purpose nicely.

A number of commercially available 55mm caps and #10 rubber stoppers will fit BetterBottle carboys and many winemakers and brewers have found them to be satisfactory; however, some have significant drawbacks (see Introduction above). If a stopper or cap has a new smell or has picked up a smell from use, it is a pretty safe bet that whatever is causing the smell will end up in the next batch of wine or beer. Use the Technical tab at the top of this page for specifics regarding Flavor Scalping.

#10 Gum Rubber Stoppers A Single-Use PE Cap A Vinyl (PVC) Cap

Low-sulfur, gum rubber stoppers (typically white) are more likely to be available as "food grade" and less likely to impart objectionable flavors than stoppers made of neoprene (typically green or black). Unfortunately, fruit juices can damage gum rubber stoppers.1  The holes in rubber stoppers should be 7/16" (11 mm) diameter. This size hole will work with BetterBottle Dry-Traps as well as most other types of air locks. A 3/8" (9-10 mm) hole will be a tight fit. It is important that the hole be molded,if possible. When holes are drilled, the stoppers should be stiffened in liquid nitrogen; otherwise, the walls of the hole may be quite rough and make a poor seal.

Polyethylene (PE) caps tend to be designed for one time use - push on and tear off.  And they are not available in ported sizes that can easily be made to fit DryTraps or other types of air locks.

BetterBottle does not recommend silicone rubber stoppers (often hazy white or brightly colored), especially for aging, because silcone rubber is so very permeable and certain to transfer flavors and chemicals.1  BetterBottle also does not recommend soft vinyl (PVC) caps, because they are likely to contain significant percentages of plasticizers, some of which are considered a health risk (see Purity/Safety under the Technical tab at the top of this page). Soft vinyl is also relatively oxygen permeable and some of the processes used to mold caps can result in rough, leaky sealing surfaces.

1 Cole-Parmer Chemical Resistance Data Base (Referenced 12/11/11)

A new 124 mm (4.88"), heavy-wall funnel for BetterBottle carboys makes filling easier than ever. It is made of sturdy, high-density polyethylene (HDPE) and fits snugly into the necks of the carboys, so there is no bubbling around the stem during fast filling and none of the slopping that occurs when funnels rock back and forth.


The special PET from which BetterBottle closures are made has a non-porous, hydrophobic surface, making it extremely easy to clean and sanitize. The O-ring in the port of the universal-style closure should be removed during cleaning procedure, so it will not become lost. The large O-ring on the both types of closures can also be removed, but this is usually not necessary. Finger pressure should be sufficient to remove the O-ring; do not use tools.  BetterBottle Closures may be damaged by temperatures exceeding 75° C (167° F). Read the Wash/Sanitize section, under the Technical tab at the top of this page, for important information. Always rinse BetterBottle PET closures thoroughly in clean water before storing them.

Abrasive scouring pads and cleansers should never be required or used.

Use only BetterBottle O-rings for replacement; they are made of special materials that cannot be easily obtained through hardware suppliers and other materials will not function correctly.

Part Numbers
Universal PET Closure (includes plug and O-rings) - BB-CLZ(PET-O4)
  • Replacement plug for Universal PET closure - BB-CLZ(PET-O4)-PLG
  • Two replacement 1/2" ID O-rings for the Universal PET closure port - BB-CLZ(PET-O4)-SERV(A)
  • Replacement Teflon encapsulated O-ring for Universal and Big Blow PET closures - BB-CLZ(PET-O4/T6)-SERV(B)

  • Port Fittings For Universal PET Closure
    90° x 1/4" Hose Barb Adapter - BB-CLZ(PET-O4)-HB2XR
    "T" x 1/4" Hose Barb Adapter - BB-CLZ(PET-O4)-HB2XT
    DryTrap - See DryTrap tab at the left side of this page

    Big Blow PET Closure with 3/4" NPT Thread (includes O-ring) - BB-CLZ(PET-T6)
    Big Blow PET Closure with 15mm BSPT Thread (includes O-ring) - BB-CLZ(PET-T4X)
  • Replacement Teflon encapsulated O-ring for Universal and Big Blow PET closures - BB-CLZ(PET-O4/T4X/T6)-SERV(B)

  • Funnel - BB-FNL(HDPE)


    Harmonized System Code - 3923.30.90.90 applies to these parts

    BB-CLZ(PET-O4) -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 3.25 lbs (1.47 Kg)

    BB-CLZ(PET-O4)-HB2XR -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 0.31 lbs (0.14 Kg)

    BB-CLZ(PET-O4)-HB2XT -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 0.35 lbs (0.15 Kg)

    BB-CLZ(PET-O4)-PLG -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 0.25 lbs (0.11 Kg)

    BB-CLZ(PET-T4X) -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 2.5 lbs (1.14 Kg)

    BB-CLZ(PET-T6) -
    Individually packed in a hang-hole, zipper bag
    Bags of 20 individual packages - 2.5 lbs (1.14 Kg)

    BB-FNL(HDPE)-124x45 -
    Individual funnels are not packaged
    Boxes of 10 funnels - 11" X 11" X 9" (26.4 cm X 26.4 cm X 21.6cm) 4.5 lbs (2 Kg)