Barrel Unions 40mm Universal for Pool FiltersBarrel Unions 40mm Universal for Pool Filters are the practical, onesolution connector your filtration system deserves. Designed to bridge 40mm pressure pipe with a 40mm 1 1 2" BSP thread, this universal union simplifies repairs and upgrades across a wide range of brands, so you dont have to juggling multiple adapters. Key compatibility and measurements you can rely on: Threaded connection: 40mm to 1 1 2" BSP Pipe compatibility: 40mm nominal bore pipe