SFI-20 certified. Sold as a Pair.; These racing over boots are SFI-20 Rated Racing Boots perfect choice for Racing. Just pull them on over your shoes, zip them up, use the adjusting strap to tighten to your preference and you're good to go! Sizing: Small 5-7 Medium 7-9 Large 9-11 Extra Large 11.5-13;.