Our PTFE High Vacuum Screw Cap Joints have been made to enable you to connect the various designs of J Young Stopcock sizes POR/5 and POR/8 without glassblowing. The stopcock arm is held rigid but can be adjusted by loosening the screw cap. Each screwthread is supplied with glass insert tubing, PTFE Insert and screw cap. For example, DSY/4/2 is supplied with 4 screw caps, 4 inserts and 4 insert tubes.