Chem-Thread, Celcon® Compression Cap with hole

The Celcon® compression caps are a convenient way of producing a grease-free connection. A Chem-Thread connection consists of three components: an externally threaded glass tube, a Celcon® polymer compression cap, and a Viton® O-ring. When the cap is tightened onto the glass tube, the O-ring is compressed downward and inward onto the metal, plastic, or glass connecting tube.  See the chart below for tubing outer diameters that work with each size.