I have the newer style RAS MK4-XXF for sale. Had them for a couple of years and they do work great. I'm like a lot of people on here that have had them, I purchased a new travel trailer and the tongue weight is so heavy, (under the max but really pushes down the rear even with the RAS) so I have purchased air bags. $175.00 plus shipping, they are over $400 new on Amazon. This is the newer style that are easier to install than the old style. I have all the installation instructions and adj disc that came with them new.