Low-friction Carbo Air blocks are lightweight, strong, reliableand affordable. Companions to the popular Harken Black Magic line, these small, compact blocks have very high working loads for safe, easy trimming. The 40 mm fiddle is an excellent choice for 3:1 and 4:1 tackles on dinghy vangs and mainsheets, as well as for controls such as cunninghams and internal boom outhauls on larger boats.