You don't want to start a crown procedure with a two-thirds empty cartridge, but it's too much to throw away. Save up to 33% on your cost of VPS impression material by combining partially used cartridges with the innovative Lock-n-Reload™ coupler. Use one coupler and an extruder gun to quickly make full cartridges from a batch of "leftovers". - Saves motion spent switching material cartridges on the fly. - Keyed design eliminates the chance of accidental cross-mixing of impression materials during refills. - Twist-lock prevents cartridge separation during transfer. For use with high-performance (rounded flange) automix cartridges. 20 blue disposable plastic couplers per pack.