100% Technora construction Significant increase in durability and performance Same function and grip as the original It's gripping ability comes from the unique hollow-braid construction For use as a prusik or Klemheist knot on ropes 7 mm or larger The 6.8mm HollowBlock2 is made of 100% Technora fiber for increased abrasion resistance and improved durability. It's gripping ability comes from the unique hollow-braid construction, for use as a prusik or Klemheist knot on ropes 7 mm or larger.