GL stopcocks, PTFE Stopcocks with cylindrical taps and GL screwthread made of pure PTFE, giving almost total chemical resistance. Can be used at working pressures of up to 6 bar when used in combination with Bola laboratory screwthread connections (at room temperature). A further advantage is that they can be used as expansion/reduction adapters to connect tubing of different diameters. For easy tubing connection we recommend accessory Bola laboratory screwthread connectors - please order separately.