The Flip jack foot come in two widths. One to fit a 2-1/4" jack, and one to fit a 2" jack. To find out what size jack you have measure the width of your jack above the trailer frame (as shown in the illustration to the right.) - A 2-1/4" Flip fits almost all standard tongue jacks (95+%). - A 2" Flip fits very small trailers and some electric tongue jacks.
With the trailer hitched as you usually tow: - If there is 8" to 10" from the bottom of the outside jack tube to the ground use a 4" tall Flip jack foot. - If there is more than 10" from the bottom of the outside jack tube to the ground use a 6" tall Flip jack foot. General Rule Average height person with trailer coupled to tow vehicle: - If the top of your trailer frame sits above the bottom of your knee cap you probably need a 6" tall Flip jack foot. - If it sits below the bottom of your knee you probably need a 4" tall Flip jack foot.