I was going to add something, but pool_dufus beat me to it. My local pool suppliers don't really like stocking the HS-1 SL because of the expiration that comes with it. We used some expired product, not knowing it was, and it quickly shrunk during the curing process. We had to tear all of it out and do the entire job again. Second time worked as expected. Be VERY mindful of the expiration date of HS-1 SL.