I am using this one https://www.amazon.com/gp/product/B01N9WLGWB/ . Bit expensive, but works great - the polyurethane foam material is firm but not hard, so ropes have just a bit of that bite into it that a human body would have (not as much, obviously). Not overly slippery either. The legs are not bendable, so no futomomo practice with this one. I never came across anything suitable for practicing leg ties, so practicing those on humans :) but other than legs - great for everything else.