This is a 550 20mm drive coupler for Kawasaki 750 / 800 conversion. It is needed to install a later 750, or 800 engine into a 440, or 550 hull, along with our conversion plate. We no longer have couplers to sell out right OR do we have couplers on the shelf ready to go. What we do is drill / tap your coupler after you SEND IT IN to us to do so. Turn around time is typically same day. ** PLEASE SEND IN YOUR COUPLER BEFORE ORDERING** Please send an email stating that you have done so. Thank you