I've been using the Proseal in the Semco cartridges. The 3.5 oz size is just enough to do three ribs in the short 2 hour working time. Once it starts to get stringy, it is hard to work with. I may have used a generous amount of Proseal, but I don't want any leaks the first time. The air powered caulking gun for Semco cartridges make the job easier and the flow stops as soon as you let off of the trigger. It makes it really easy to put Proseal on the shop heads.