Speck Pumps EcoMV Pump Union [3" w Adapter] (2921770005) partypool and SherLok compatibility together with and SherLok compatibility together with the 2 inch relationship give this tank body its practical value because structural filter parts work best when they match the original size and assembly relationship closely Helps avoid replacing larger assemblies when the correct individual part can be identified Speck Pumps EcoMV Pump Union [3" w Adapter] is a Speck pump union component used to create a serviceable connection in compatible pool and spa plumbing systems and equipment installers working with compatible Speck pump models