Bellco compression fittings are designed using our standard 45mm blue polypropylene open top caps and white silicone gaskets. A wide variety of fittings are available to allow ph and do monitoring via insertion of these probes into sidearms or vessels. Bellco probe adapters are designed to allow introduction of threaded probes into vessels through 200mm stainless steel or a 45mm vertical sidearm. 316l stainless steel Size: 1/2 inch