We use these (and the white versions) exclusively now to hang scenic cloths and gauzes in our community theatre. In our case the drop is only 3 metres (11 metres width - work in that one!) but they hold very well and there are no concerns of slippage. These days we just leave them attached to the cloths, rather than removing (which you can) and buy new ones for new cloths because the volume price breaks at Thomann make this cost effective.
The plastic is a decent tough type, not brittle or flimsy.
When received they are each attached to their injection mould plastic former: so get yourself a comfy chair in the evening, a cup of tea and something watchable on the TV and prepare yourself a bag full of them ready for use. It doesn't take long. Oh, and if you find out the use of the thin ribbed panel piece then let me know, it's not needed anywhere!
Recommended.