Ronstan's Series 40 Blocks have maximum working loads between 770 and 1100 lbs., depending on the block configuration.
Sheaves are1-1/2 in (40mm) precision-molded, UV-stabilized Acetalﾠwith Acetal ball bearings and support a maximum line size of 3/8 in (10mm).ﾠ High-load (HL) blocks can handle wire to 5/32 inch in diameter and have extruded Nylatron sheaves. The pin diameter on these blocks is 3/16 inch.
Use these blocks for vangs, backstays, cunninghams, traveler controls, furling line leads and main/jib/spinnaker sheets. They work well for mainsheet, jib sheet, and control line situations on boats up to 26 feet.
This double block has a universal head that can be fixed in-line or perpendicular to the sheave, or left free to swivel and a becket for cascades.