Residential spring safety break device,adjustable and unadjustable type 

spring failure safety device protects and adjusts door operation,in order to stop the door drop..

1'' bore and the other type is for 51 and 67 spring fitting 

CAUTION: Installing or repairing 
garage door can be dangerous task. Garage door springs and cables are under
extreme tension and require appropriate safety precautions. Working with
garage doors and openers could result in personal injury or death. We recommend all installations,
repairs, adjustments, and removals on garage doors be made by a qualified
garage door technician. Any attempts to install, repair, replace, adjust garage
doors or openers are done at your risk.