The Harken 40mm Carbo Air Fiddle Block with Swivel & Becket - Fishing is a top choice for dinghy vangs, mainsheets, cunninghams, and internal boom outhauls on larger boats. With a sheave diameter of 40 mm and a maximum working load of 220 kg, these lightweight and durable blocks are affordable and reliable. They are a great companion to the popular Harken Black Magic line, offering high working loads for safe and easy trimming.