They feature 48mm sheaves of high-impact black plastic with deep V grooves for the cord. The steel axle is riveted to the frame, resulting in minimal friction. Sheaves are wider at the hub to limit contact between sheaves. Ample space is allowed at the top and bottom of the block for stringing cord. Riveted frames can support more weight than schools normally use and come with eyes at both ends.
(
;){kind=link}