Pro Circuit 4 X 1.5 Canister Quiet Insert PC4012-0007 The Pro Circuit Stainless Insert is available in multiple sizes to make your motorcycle quieter, without the loss of power. These inserts are available for both the 4in. canister and 3.5in. canister. Call for applications Note: 2007/2008 Stainless Inserts will NOT fit older model end-caps