03.06 38mm Single Block with V-jammer03. 06 38mm Single Block with V jammer These are tough general purpose high load blocks. They have a similar classic design to the 25mm range but have very high load carrying capacity. Their simple construction and plain bearings means they are long lasting and require very little maintenance. Rope Sizes & Types: Up to 10mm; standard 3 strand or plaited nylon, polyester and polypropylene ropes. Sheave: Tough "Arnite" plastic Bearing: Plain low