The SMAI X-Frame Barbell sleeve, otherwise known as a Torsonator or Core Trainer, is simple to use and solid in construction. Used in conjunction with an Olympic Barbell, you simply attach the Barbell Sleeve to the X-Frame and slide the barbell into the sleeve. This creates a functional new design that allows for manipulations to your training. Will fit any 65mm x 65mm steel tube with 25mm hole.