NEW Grundfos Pump Retainer Neck Ring White gasket spacer 1-3/4" OD 405134 CRK2 OD of ring is approximately 1-3/4" I am not 100% sure of the part number of this, but it was with other 00405134 kits. So I assume is was part of this. THis is awesome and this model they do not make anymore. You should get this, before its gone forever! I dont see this anywhere on line I got this at a company overstock auction. they opened the box and let it sit in the warehouse for a long time. It collected dust and may show shelf wear. This will work or money back. PLEASE NOTE- I am not familiar with these systems. if you know more let me know!! You are getting what you see pictured! FREE USA SHIP