I did a lot of research on this. Went to Amazon as well as RV Net. Wish I could remember the name of the ones I bought. Mine are flexible and clamp to outside tire, which tire people can not guess this clamp tight enough on the rim. A lot of the ones I read about would soon leak. mine are heavy braid and have been good thus far. I have about 17,000 miles on the truck so not a long term test. Go to Amazon as well and read the reviews. Next time around I might try the solid extenders. However mine are great as long as the clamp is tight. Course its a little hard to get a wrench on the nut.