Aftermarket for Senco SN4 SN70 Bumper BB0018Bumper / Piston Stop p/n BB0018 For Senco SN4 SN70 SN3 AST4 Framing Nailers Price includes Shipping in the US Ships USPS Package Rate with online tracking. Post navigation Senco SN325 Framing Nailer Rebuild kits SN4 O-ring kit + LB3500 + bumper BB0018