For the saddle mounts to fit the racks, the crossbar of the rack needs to be 3.5 inches or less. The thickness of the crossbar needs to be more than 1/2 inch or more (my aftermarket crossbars are 3/4 inch on my Grand Cherokee). This is probably the limit for any weight you would put on the rack anyway.My hull is 27 inches wide. The kayak needs to be loaded right side up (it has drains to get rid of rain) and the inside edge of the saddle mount on the bar was 23 inches from the left to right saddle when mounted securely.This, with the tiedowns, makes for a very secure attachment to my Grand Cherokee.The kit came with long bolts. I had to cut them (very carefully to preserve the threads) to 1.75 inches to make room for them to be installed. This also makes removal from the crossbars much easier (I need the crossbars for hauling plywood). To keep the bolts from getting lost, I put a piece of Tygon tubing on each of them.