Marine supply support plate distributes outboard engine weight to protect your transom and distributes the stress of the motor mounting bolts and can allocate loads on high -performance engines more evenly Transom Support / Washer Plates are made of strong Aluminum alloy (not cast aluminum), the CMC transom washer can eliminate bolts "biting" into transoms resistance to corrosion and rust Fits lower bolt pattern of outboard, 10 IN bolt hole pattern, 0.427 IN thick You need to use your own bolt and washer to install the plate (Package only includes one plate) .