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. They have the rounded edges so are legal for rugby. These are made of polyurethane and will fit in rugby, soccer, football, and lacrosse cleats with "standard" #10-32 threaded inserts but will NOT fit those with specialized threads like Adidas Malice, Adidas Predator, Canterbury Speed 2.0, Gilbert Prolite.