The Alpi system is an Italian system of advanced studs. Important: To open and close the studs, use the key provided. This anti-slip solution allows you to easily angle the studs out from under the shoe when the surface becomes slippery or when extra grip is needed. A pair of shoes with studs is the ultimate in ice, snow or just wet and slushy conditions. In addition, you can easily and quickly fold the studs with the key, so you don't have to wear the studs if the surface doesn't require it.