The Antal Barber Block is a snatch block with a low-friction-ring head.
It provides an immediate entry of the sheet (the cheekplate revolves around the sheave axes allowing the block to open) along with an easy 2:1 control (a line through the ring allows the adjustment of the block height).
A safety ball stops the cheek plate from opening, a small becket allows the connection of a hanging line, rubber covers protect the deck from bumps.
Aluminum sheave with CF bushing and side ball bearings.