I just installed a set of polyurethane boots on my CB550k3 and they are great. Much easier to work with as they are very forgiving compared to the old rock hard rubber boots, will not harden over time & are fuel resistant. They are a little more slippery, when tightening the first clamp the bottom of the boot slid off. Just had to be careful & hold them in place when tightening the clamps down. They seal very well on the airbox. I was also advised to check them every once and a while, if the motor moves around they can slide off the carb, not likely, but will keep an eye on them. Overall I am very happy I spent the $30 + shipping.