You are looking at a NEW, "Sand Foot" for your trailer jack. It fits almost all standard trailer jacks from 1,000# up to 5,000# with the standard round tube body. It attaches with a 1/4" spring loaded hitch pin for easy on, and easy off, into the existing hole in the bottom of your jack. Zinc plated for rust protection.
The ID of the mount is just over 2 1/16" to slip over a standard 2" jack. This jack foot is almost 9" tall overall, with the attachment pin just over 8" off the ground. If your trailer has a high tongue, this will extend the jack 8" so you don't have to put blocks under it every time you jack the trailer, and saving about a "bazillion" cranks of the jack handle just to get it down to the ground!