Despite what some say, bigger is better, and if making something bigger is easy, that's the best! A big bore kit is an easy way to achieve more displacement, and if you can install it without rebalancing flywheels or boring the crankcases, that's about as easy as it gets. That's the idea behind the new S&S® 106" big bore kits for 2007-up big twins. 106" Big Bore Kit, Includes Piston set, top end gasket kit & S&S cylinders 3.927" Bore, 4.937" cylinder length & 4-3/8" Stroke. For 2007-up Harley-Davidson® big twins.