This is a Novarossi 41016 Medium Conical On Road Manifold. This 6-ring medium length manifold is recommended for .21 class on road engines, and tracks that require a balance of top and bottom end power delivery. Package includes two gaskets, one long spring and three short coupler springs.
Conical vs. Non-Conical:
Conical manifolds have a tapered inner diameter that gradually increases throughout the length of the manifold and will produce more power than a standard manifold at the expense of decreased runtime. Non-Conical (or standard) manifolds have a consistent inner diameter throughout the entire length of the manifold and will provide smoother power delivery and better runtime than a conical manifold.