Radium Engineering 20-0087 O-ring Service Kit is compatible with both variations of the "standard" (4" OD) fuel surge tanks (FST and FST-R).Variation 1:Small O-rings for M5 bolts (x16) and large O-rings for canister (x2).Variation 2:Gaskets for canister and bolt holes (x2). NOTE: Bolt holes seal with gasket.