Material: stainless steel/titanium 

Locked with proprietary screw. comes with 2 screw keys.

Hook Gauge option: 2mm, 3mm,4mm,5mm,7mm,8mm,9mm,10mm.

S style option's U shape inner diameter: width 15mm, height 13mm

L style option's U shape inner diameter: width 21mm, height 16mm

custom style option to allow you customize size of U shape, or even the shape of hook.
For some special custom dimensions,it may can't be made or would need to charge a little extra, if this happens,will contact you.