The 10mm female to 14mm male glass converter also knowns as a reducer is a glass attachment that is typically used to reduce a 14mm female joint on a rig or bong.  

For example:  If you have a 10mm male banger that you would like to use on a 14mm female joint, simple place this converter into the joint and then you can use your 10mm male banger.

Specifications

• Height: 2.75 inches
• Glass thickness: 3mm Borosilicate Glass
• Joint size: 10mm/14mm

NOTE:

The outer part of this converter is 14mm male.  The inner part (where the bowl or banger goes) is 10mm female.

So you would need a 10mm male banger to fit inside of it.