Abstract: An improved gas riser comprises a pipe nipple, casing, adaptor sleeve, tube, and stiffener. The adaptor sleeve features an internal stop which accurately positions an end of the plastic tube before the tube is plastically deformed into grooves in an internal surface of the adaptor sleeve. Each of the first and second ends of the adaptor sleeve can be manufactured in different diameters to fit pipe nipples and casings that are required by different code regulations.

Abstract: A collet for gripping an associated cylindrical workpiece comprises a pair of actuating rings and a plurality of slide blocks. The slide blocks are held within a housing and feature a pair of opposed slots within each slide block. The slots are oriented at a 45.degree. angle to a radial centerline of the slide blocks. Each one of the slots slidably receives one of the actuating rings therein. Axial movement by an actuating ring causes radial movement of the slide block inwardly toward the workpiece to grip it, or outwardly away from the workpiece to release it.