Flex Couplers come in half sizes from #2 through #7. Each half size changes the gap by 1/32″ (thus a full size changes the gap by 1/16″).
The smaller the Coupler number, the larger the gap. Flex Couplers use the same shank sizing as Reeves sleeves as this is the industry standard for shank sizes.
If you’re unsure of where to start, we recommend you buy one each of the most commonly used Flex Couplers (4.0, 4.5, and 5.0) as a great way to get started.
Flex Couplers will only work on mouthpieces that have been converted for use with