GL45 Port Cap Kit, reinforced Stainless Steel 1/4-28 UNF threads, PTFE inner, blue spin collar, designed for use with 45mm media bottles. Fits glass bottles with a GL45 (45 mm) neck size. 304 Stainless steel (SS) threaded insert minimizes cross-threading on soft PTFE ports and is ideal when tubing adapters are regularly removed and re-attached.