Garage door torsion spring fitting is used to fix the garage door torsion spring 

Size:2'';2-5/8'';3-3/4'';5-1/4'';6''

Universal for lift and right spring winding

1 pair consist of a mobile and stationary parts

Hand spring diam.(MM):45;50;67;95;135;152

Dia. shaft(mm):25.40

Garage Door Adjustable Top Bracket,there are commercial type and residential type 

Garage Door Adjustable Top Bracket with galvanized steel./2.5MM for 11MM shaft.Montain holes on 4-3/4'' centre (vertically) for 7/16'' diameter stem roller residential top bracket support galavanized too,1.5MM ,adjustment 3/8'' max;mounting holes on 3'' centers (vertically)

So it works for safety,very important for garage door system safety protection.
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.