Low-friction Carbo Air blocks are lightweight, strong, reliablend 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.