Had fun today. Not really. Spent a few hours on my roof installing 20 feet of ICC Excel pellet vent. Then taking it all back out...then half of it back in again. There appears to have been a design change somewhere along the line for the Excel vent pipe gasket. I have five sections of 48" vent. Four pieces had a floating silicone gasket. It just sits in the groove in the inside of the pipe. The other piece of vent pipe had a bonded-in-place silicone gasket of a slightly different shape. The one with a bonded gasket also has dimples where the inner and outer parts of the pipe are spot welded together. Even though I used copious amounts of dish soap to lubricate the gaskets, they where a VERY tight fit. I was careful to line them up and gently twist as I put the ends together. After it was all installed I went in the house and looked in the fireplace and saw a bunch of chunks of silicone gasket. Not happy. The pipe with the bonded gasket went together much easier. I took all of the pipe apart and found two of the floating gaskets had been cut into chunks. I brought all of the crap off the roof and into the garage. I scavanged a gasket off another fitting and took the one out of the top piece at the cap. I cleaned the inside of the pipe at the groove and put some red RTV into the groove and inserted the gaskets. Hopefully they will stay in place once they're glued in. I'll give it another try in the morning. I'm still PO'd. I don't know which is the newer design. Both types have the same model number.