5 mm neoprene.
The seams of the boots are waterproof due to GBS assembly (Glued and Blind Stitched): the neoprene is glued and then stitched for maximum resistance (the needle does not go all the way through the neoprene to prevent water getting through).
A latex sole: this increases comfort when walking, durability and, therefore, the lifespan of the product.
How to choose your size
Try them on with your fins. The fit should be as tight as possible.
These scuba diving boots provide thermal protection that has been tested by the independent INPP institute (Marseille, France) in order to validate their compliance with the current standard (EN 14225-1:2017)
Good Value for the money but very tight. I am UK size 9 (43) and bought the size 9.5 to 10.5 and they were still slightly on the small side. Now I'm replacing with a different brand as these ones have holes on both heels and splits down the side. I think this is partly because they were too small and possibly also because I often walk 5 mins from car to beach in them, and always walk over a Stoney beach to get to the water.......won't really know for sure until I see how the next ones fare under the same conditions