Holt Nautos Line28 Single Fixed Head with Becket HT92515

Real performance even in the small blocks has always been a Nautos principle.This series of blocks is evidence of this.
Rollers over a hard axle handle a greater load than  ball  Bearings - 

Optimist Halyard Block with Becket

20 MM SHEAVE DIAMETER
MAXIMUM LINE DIAMETER 1/4" // 6 MM

LENGTH  50 MM 
WORKING LOAD 280 LBS
BREAKING LOAD 1100LBS