This is a great kit from CE Smith Co. It comes with everything that you need to install the side guide boards on your trailer. It will fit trailer frames up to 3 inches wide and 4 inches tall and anything smaller. These guide on rails will make loading your boat a snap by yourself or in windy conditions. The kit has (2) 2 ft x 4 inch x 24 inch long pre-carpeted boards to guide your boat. The posts are 21 inches tall and can adjust about to 13 inches wide on each side. They have a 75 degree angle to them. You can also mount the guides above or below your trailer frame for extra adjustment so that they can meet your boat at just the right spot. The side bunks are mounted towards the rear of your boat trailer to assist you in lining up your boat on the trailer. This 2 foot length is ideal for smaller boat trailers and jet ski trailers.