PREMIUM AUTOMOTIVE HEX HEAD SEMS BODY BOLTSAuveco 12066 M6-1.0 x 25mm Hex Head SEMS Bolt with 24mm Washer OD – Phosphate Finish. Head Type: Hex SEMS. Length: 25mm. This bolt features aSEMS design (captive washer) that distributes load evenly and improves fastening strength while reducing loosening due to vibration.