Basic Guide on Glass Joint Sizes

Last updated: March 1, 2026

Buying a new bowl, downstem, or nail? You need to know your joint size and gender first. Here's a simple guide.

What Is a Glass Joint?

A "joint" in the glass world (different from a rolled joint) is the point where two glass pieces connect — such as where a bowl connects to a bong, or where a nail connects to a dab rig. Joints come in specific sizes and genders. Buying a mismatched piece is one of the most common and frustrating mistakes in glass shopping.

Joint Sizes: 10mm, 14mm, and 18mm

Joint sizes refer to the inner diameter of the female joint (or outer diameter of the male joint). The three standard sizes are:

10mm

• Small, compact size
• Found on mini bongs, micro dab rigs, and small pieces
• Best for small dabs and low-volume use
• Bangers, bowls, and tools must all be 10mm to fit

14mm

• The most common size across the industry
• Found on the vast majority of mid-size bongs, dab rigs, and water pipes
• When in doubt, measure — many pieces are 14mm
• Widest accessory selection available at this size

18mm

• Large diameter, used in big bongs and high-flow pieces
• Best for large water pipes and high-volume use
• Less common in smaller, portable pieces

Male vs Female Joints

Female joint: Has an opening that accepts a male piece inserted into it. Most bongs have female joints — the bowl or nail slides inside.

Male joint: A protruding piece that inserts into a female joint. Less common in bongs but standard for certain rigs and accessories.

How to Measure Your Joint

• Use a ruler or bring your piece into the store
• Measure the inner opening diameter of the joint
• Check if your bowl/nail slides in (female) or over (male) the joint
• 10mm: roughly the diameter of a pencil
• 14mm: roughly the diameter of a dime
• 18mm: roughly the diameter of a nickel

Bring your piece to 535 Smoke Shop and our staff will measure it and find the exact fitting bowl, nail, or downstem for you. Call ahead: (407) 778-1326 (24/7).