Details Keep your toes warm and your feet cozy with the O’Neill Heat 3mm Socks. These socks are great for layering with round toed booties, keeping your feet toasty on the coldest days. You can also pair them with any type of swim fin in cool to frigid water to get a snug fin fit and warmer toes. Made with no sole or tread they will slide into booties or fins easily for an extra layer of insulation. O’Neill has always put their best foot forward when it comes to innovative product invention and design. These comfortable neoprene socks are no exception.