Spectre Performance 9603 3.5" Filter Adapter;

Spectre’s air filter inlet adapters and velocity stacks are designed to allow you to attach a larger 6 inch diameter flange air filter onto a smaller diameter air intake tube. The velocity stacks are available with different neck sizes, to match 2.5 inch to 4.5 inch tubes. In addition, Spectre velocity stacks also have a smooth funnel shaped inlet that reduces restriction and turbulence of incoming air.