A2020XHL 20mm Allen Pulley 20mm Single Extreme High Load Block XHL blocks have been designed to deal with extremely high static loads without compromising on low load dynamic performance. Ideal for use in vang cascades or halyard turning points where static loads can be extremely high but low load fast rolling speeds are required. XHL Bearings - Twin rows of stainless - steel ball bearings running on a stainless - steel axle with the addition of a protective plain bearing washer. A key feature within the XHL bearing system is the precision plain bearing washer. When the XHL is exposed to extreme static loads (which would normally cause damage to the internal bearing system) it changes to a plain bearing block. This stops the ball bearings from getting damaged and thus no longer performing as designed. As soon as the static load is reduced the XHL returns to a high - performing dynamic block. Body - The aluminium body features "ears" at the top of the block. These are to be used when attaching the block and stop the block from capsizing when under load. Sheave - The stainless - steel sheave allows the block to be paired with both rope and wire. ALLEN EXTREME HIGH LOAD A2020XHL Technical documents can be downloaded here