These 1/2 inch long plastic screw-ins are great for hard ground or synthetic surfaces. Don't buy a whole second pair of cleats, just change your studs when you go from soft grass to firmer or synthetic surfaces. Also great for sevens play. These are made of polyurethane and have standard threads that fit most cleats. They will fit in soccer, football, and lacrosse shoes too. They have the rounded edges so are legal for rugby.