These Grand Rock Stack Installation Bed Kits are the stack installation kits only. Tell us what size of stacks you will use the kit to install, so we can get you the right size stack clamps. We also need to know what size the exhaust is that you will be hooking up to. Kits for Exhaust Diameter/Sizes 2.5", 3" and 3.5" will add the reducer and clamp you need to the installation bed kit that matches your stacks. Kits for Exhaust Diameter/Size 5 inch are made with all 5 inch piping. These Grand Rock Stack Installation Bed Kits are heavy duty commercial grade aluminized exhaust parts from Grand Rock!