This is a A-904-610 Nut, Disc Mower PN: 904-610Main Description As Following : A-904-610 Nut, Disc Mower P.N: 904-610 Bolt Diameter: .704" around the base.Replaces: 526905 Crossed From: 526905 MISCELLANEOUS Found in Section & Models : Hay Tool Parts > Disc Mower Blade Bolts & Nuts, New Idea MOWER, DISC: 5209 (SN 9756 - 16012), New Idea MOWER, DISC: 5212 (SN 9756 - 16012), New Idea MOWER, DISC: 5312 (SN 9756 - 16012), New Idea MOWER, DISC: 5406 (SN 9756 - 16012), New Idea MOWER, DISC: 5409 (SN 9756 - 16012) Associated Items : A-904-606 Also This is An Aftermarket Product And : Bolt Diameter: .704" around the base. Replaces: 526905