I didn't have any issue with the new bolts, the problem was that the old ones just broke off when I tried to remove them. Then I had a little stubby end of two bolts holding the valve in place, with no way of pulling it out except for drilling. To actually get at the bolts I had to get the old valve off/out of the canister and that was impossible with the bolt remnants still in place. The whole canister is plastic with just a bit of metal around where the bolts are. Heating it up with a torch was no good, considering the fact that the canister has been venting gas fumes for ten years into charcoal, I didn't consider heat an option. So I cut the old valve off carefully with a hack saw. I cut on either side of the valve separating the valve from the bolts. That way I could pull the valve out while the bolts were still in place. I thought this way I'd get another crack at attempting to rotate the bolts out with vise-grips. That proved to not work as the bolts just eventually broke off. Then all I did was grind down the bolt remnants and re-drill the bolt holes with a smaller size. Then tapped the holes for smaller bolts. Normally I'd go larger and get rid of the old rusted metal, but I wasn't sure how thick the metal inserts were. Also the valve doesn't require a lot of bolt strength as the valve sits in there tight without the bolts. I figured that the first valve lasted 10 years, I assume the next will last that long.