Set of Three 5/16, 3/8 and 7/16 ARP Rod Bolt Extensions A long taper and full radius prevents nicking and scratching of crankshaft journals during connecting rod installation. ARP rod bolt extensions act as a guide during piston and rod installation they will also hold the bearing shell in position in some applications. Available in 5/16, 3/8 and 7/16 extensions are packaged in pairs and are hard anodize color coded for ease of identification.