Screw links are the perfect solution for situations where a more permanent attachment is needed, or where speed is secondary.  They work great on the end of your ascenders, at the tops of towers, distributed slings and chest harnesses.

This is the Semi-Circular style, favored by many for linking chest and sit harnesses, and distributing load.  Constructed of 10mm steel, these Cypher links have a working load of 900kg with a rating of 25kn on the major axis.  CE certified.  Quantities limited.