BIG-SERT M14x1.25x15mm TAPERSEAT INSERT QTY 2 # 51455 BIG-SERT OVERSIZED REPAIR for use when a helicoil has failed M14x1.25x15mm Taper seat spark plug insert Professional repair insert for a high quality repair Solid bushing oversized spark plug insert must have kit p/n 5141S or 5141E to install.