The loops in stock are from Unicycle, a french company.
National Theatre of Scotland have 4 Amspec hand loops with keys and 1 without a key.
16 hand loops were bought for Spring Awakening.
Accurate on 01/04/2018
Just like harnesses hand loops should be checked on a regular basis when in use. The ones in stock at RCS are of the same composition of a round sling. Made of polyester
1- Label is readable and date of manufacture is within 10 years.
2- Run hand around the whole circumference feeling for any deformities and checking for any cuts or nicks.
3- All stitching should be intact and not frayed.
4- Key should move freely along loop.
5- The loops must be thoroughly examined every 6 months by a competent person. 
The hand loops had keys and performers would climb each frame or sit on the swing and secure themselves into the hand loop and then hold on to the loop. Each loop was repositioned and given a visual inspection before every show.