BILLET ALUMINUM TAILHOUSING SPEEDO PLUG Tremec TKO, 3550, T5, T45 & T56 Magnum Speedometer Block Off Plug This plug will block off plug the mechanical speedometer port opening on Tremec TKO, 3550, Borg Warner T5, T45, and the T56 Magnum transmissions. If you're running an electronic speedometer this is a must have and machined out of billet aluminum. Includes the o-ring. Does not include Bolt