Distributor Oring 1.05" ( also called 1" )
Used on Fleck 2500, 2700,2750, 3600, 9100 and 9000 Valves.
Also, common for many newer ( since 2003 ) MacClean / CUNO Valve body / adapters ( such as CEC 1000 )
NOTE: Same o-ring is used on Clack BY PASS ( V3006 ), and all "Fittings" used with Clack valve or Bypass. Also Clack Valve Meter Plug ( V3003-01 ).
Their part number for this o-ring is V3105.