If you have a mast step or mast heel plug with a tenon you will need one of these in the bilge or on the deck to receive it. RWO's stainless steel mast step is 5 7/16 in. (138mm) long with an inside track that is approximately 3/4 in. (19mm) wide. It comes with two clevis pins that can be set in various holes to prevent the mast step from canting forward or aft.