Like the 5 Series blocks, but with Schaefer's ball-bearing sheave. Curved ball races allow Schaefer ball-bearing blocks to take higher loads than other similarly sized blocks.
A flat, stainless base plate distributes load to a larger surface area than other designs which place loads on mounting bolts only. Use spars and decks to lead sheets, halyards, reefing gear, and any control line requiring a strong, smooth lead.
