The BISupply Swivel Top Boat Trailer Bunk Brackets make launching and loading your boat a breeze as you nestle the bow into the bunk. Our bunk brackets are manufactured from 11 gauge zinc-plated galvanized steel to resist corrosion in both freshwater and saltwater environments. Compatible with 3 x 3in (7.62 x 7.62 cm) cross members, included U bolts are 1/2in (1.27cm) thick, 3in (7.62cm) wide, and 4-5/16 (10.95cm) long. Industry-standard 8in (20.32cm) board brackets boat parts feature slotted holes for precise adjustments to your boat. The swivel bunk boat trailer accessories hardware kit includes 4 rectangular brackets, 4 trapezoid swivel top brackets, 4 U bolts, and all hardware for jet ski bunks and boat trailer bunk supports. Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.