B&M Racing & Performance brings you this billet aluminum speedometer port block-off plug that fits GM TH350, TH350c, Powerglide, Muncie M-20, and Aisin AY6 transmissions. This 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 hardware and instructions for a quick and easy installation.