Multiblocks are covered under the same patent as the regular P-Bar Blocks. Identical in size and composition, on Multiblocks the raised rail can be detached from the block. Hook and loop fastener tabs along the top and bottom of the blocks allow you to stack the blocks one atop the other to turn high bar into a trench bar or lie them on their side and actually be able to take a few steps while spotting an athlete on beam. Our general rule of thumb for recommending which style of P-Bar Blocks a gym should purchase is based on desired use of the product. If you are using them primarily for training boys in P-Bar skills and as occasional spotting blocks, get the traditional style. If you are looking for a great boys training tool you can also use as supremely versatile spotting tool, get the Multiblocks style. Dimensions are 27 x 51 x 39 with a 1.5 high simulated rail of special composition foam making the swinging height 40.5. Each block weighs less than 50 lbs, thus making it the lightest, most portable spotting block of its size.