The COBB Delrin Oil Cap's construction of pure medical-grade black Delrin means it does not absorb heat like many aluminum options. The included seal and shims ensure an OEM-like fitment and guarantee proper orientation. It's fluted design around the edges provides excellent grip. Have you noticed the fingerprint recognition on your mobile device does not work after having to add oil to your Subaru at the track? The COBB Delrin Oil Cap will not absorb heat like it's metal counterparts - thus eliminating the fear of searing those precious digits.