I bought this undergarment for a recent Red Sea trip with water temps in the 68-72F range. It was the comfortably warm for recreational dives <90 mins, but I also tolerate cold well. If you get cold easily you might want to layer with a warm base layer (e.g. merino wool) or go up to a 200 weight garment; there were certainly times where I could tell the temperature dropped from the 70s to the 60s.I am 6'1", ~205 lbs with longer legs than torso and purchased an XL. It was a little snug so if I'd had more time I probably would have gone up a size, but the garment stretches enough that it wasn't a problem. The only reason I dropped 1 star was because the fabric has started to pill up, but I also did 25 dives in a short time on the trip so there was a ton of donning/doffing the drysuit.I definitely like the 2 way zipper (zips from top or bottom) because it makes it much easier to use the restroom and set up a P-valve if you're thinking about doing that.This is a base layer, as in not a lot of warmth given. It is great for movement and shedding perspiration. I am the most comfortable at 68F to 76F water in a trilaminate dry suit. I also live in north Alabama so anything below 70F is cold to me. For what this is, it is great.I'm writing this pre dive. I bought this for warm water drysuit diving 50 - 72 degree water temps. It's not very thick seems like it's going to be comfortable to dive. I'll update my review post dive. Thermal cline is about 60 in 25 feet. Post dive review. This thing is perfect for summer diving In a dry suit in New England. Watch the size they run small.I would say this is equivalent in thickness to a pair of long underwear. I got it because it reduces boyancy. Its comfortable and fits well but I would say min water temp of 55+.I had purchased this item with the intent of wearing under my dry pants & dry top for an extra measure of protection while cold water kayak touring. The product description indicates "repels water" as one of the headline features, which lead me to believe it would help to keep you dry if water did manage to find a way through the first layer of protection. This is not the case. I also purchased the product in an XXL, which would normally work for my 6'6, 220# frame. It is a tighter fit than I would have expected. I have not tested in extreme cold yet, but I do believe it will help with keeping me warm. Fortunately, the product was deeply discounted from original purchase price, and I had an Amazon gift card which paid for most of the cost.I can't complain about the quality of the garment, but size chart isn't accurate. I am 6'2" on the nose, and the XL was listed as fitting me. It didnt, it was too short, fitting someone 6' comfortably imo.like ease to get in and out of your dry suit so you can you dredge for alaska goldA little lightweight for cold water diving but otherwise well made. Just wear another layer under itFits well