3.00" ball bearing blocks feature large-diameter, free-rolling sheaves. They are used on scows, catamarans and iceboats, as well as small offshore boats. The 2.25" is the original and still the most popular block in the Harken line. 75mm blocks feature Torlon roller bearings and carbon-black balls for strength and reduced wear. Fiddle blocks build simple three and four part purchases. Their large sheave/small sheave configuration prevents line chafe and ensures a low-friction tackle.