I've been using the 635/556 combination for several years now. I'm on the third boat with this combination and will be fiberglassing the newest hull on friday. This is what they call their 2 to 1 slow non blushing. I've never had any problems with blush. The epoxy has cured out very durable. It has a long pot life and a longer curing time. They are not exagerating on their site when they tell you the pot life and curing times. I like it that way, though. I believe in slowly going fast. I'm in Texas so it gets hot here. I've used this epoxy up to over 100 degrees. I've only used their 6 oz cloth, but I'm happy with it. It wets out nicely. Clarity for me has been fine. I will be trying other weights later. If you order more than 10 yards it comes on a roll, not folded. They have called me after the order to make sure I know what I'm getting and how it works. The prices have been good. Check out the fillers and other stuff. I've also tried Raka during this same time frame, but prefer the USComposites stuff. I'm happy with them. Will probably stay with'em.