The plastic heel cup protectors provide comfort and protection and relieve heel and lower leg pain for jumpers, hurdlers, runners, and walkers. Unlike athletic shoes, M-F Heel Protectors (Plastic Heel Cups) never wear out. As shoes provide less support, the M-F Heel Protector takes up the slack. M-F Heel Protectors are lightweight, but they absorb blows and will not fall apart or deteriorate after constant use. The material is exceptionally strong, very pliable, and ultra thin. Fits comfortably around the heel – can be worn over or under a sock. Proven performance since 1960 at a reasonable price! Regular size for adults – fits 96% of adults (Red Star on heel).Junior Blue star is for Small or Children aprox size Womens 7.5 of less.Can be molded by placing under hot water for a minute then applying.