Billet aluminum construction with hard anodized black coating. Easy upgrade when changing tappets or doing a cam change. Improve tappet stability in high lift and high rpm situations. Factory tappet guides are constructed of plastic and are at risk for allowing tappets to twist under heavy stress, these tappet cuffs capture the tappet without impacting vertical motion to keep them aligned without twisting. Made in the USA. Due to variances between cam and tappet manufacturers, always check the tappet-to-tappet cuff clearance..