What is the difference between the thicknesses of the MACE manifold insulators (6.35mm, 12mm, and 25mm)?

The main difference between the manifold insulator thicknesses is the level of torque increase they provide: 6.35mm – around 10% more low-end torque, 12mm – around 13% more low-end torque, 25mm – around 15% more low-end torque across a broader range.  The 25mm option delivers the greatest improvement in low-end torque by effectively increasing the runner length. However, before selecting a thickness, we always recommend measuring the available clearance under your bonnet to ensure a proper fit.