RTS brings you this billet aluminum speedometer port block-off plug that fits GM, TH400 transmissions. The plug is used to block the mechanical speedometer gear port when upgrading to an electronic speedometer and includes a replaceable Buna-N rubber o-ring. It features a black Mil-Spec anodized finish for long lasting good looks, even in harsh conditions. Comes with installation instructions for an easy and quick installation. Features: Fits GM, TH400, (For Chevrolet model transmission only. Will not fit Buick, Oldsmobile, or Pontiac model) Billet Aluminum Construction With Engraved RTS Logo Protects Your Transmission From Contaminants during use or storage Replaceable O-ring Seal for leak prevention and simple maintenance Perfect for Electronic Speedometer Conversions Includes stainless steel hardware for superior corrosion resistance