Turbo Switch Grip Empty Inner SleeveBlank Inner Sleeve for use with custom thumb molds with 1 diameter or your own 1-1/4 thumb solidsThere are two locking tabs at the bottom of each Inner Sleeve, one tab is slightly larger/wider than the other to ensure the Sleeve can only be inserted one way into Outer Sleeve. This prevents the Sleeve from being put in backwards or upside down.The locking tabs are designed to withstand up to 180# psi. While they are certainly built to perform, like most consumable and movable products, the Inner and Outer Sleeve locking mechanisms will wear over time. There are many variables that influence how the product will wear including grip pressure, # of games bowled, # of times insert is being removed/interchanged, proper use and storage, drilling etc. Please be sure to visit your retail professional for a fit inspection periodically to ensure best results and performance. Requires Switch Grip Outer Sleeve – Sold Separately One Inner Sleeve per unit