In reply to SarahHarrop:
Made my own out of the prowire crab and mammut slings. They are lovely!, not these cheapest though. Recommend the same although maybe change the sling if you want cheaper. Prowires are cheap and light.
My slings are 30cm, perfect for trad, if I want shorter slings I can double the slings over and halve the length.
For the rubber band mentioned earlier go for sheep castration/lamb docking tail rings. About a quid for 100, avaliable from farming supply shops.