I x 1.2m (waist / abseil backup) and 1 x 2.0m (foot loop). Both in 5mm cord. Tried 6mm cord and it doesn't bite as well. I'd not trust 4mm cord. I've tried these lengths as self rescue dangling from end of rope as if fallen off traverse, and they work well on both single and one half rope. French prussic on the short one and klemheist on the foot loop.
Out of interest, how many have tried ascending on their own chosen setup?
> I have a short one, enough for a 6 wrap. Then I have much longer one, long enough to make releasable through a munter mule.
I do as needvert. I carry one long and one short.
One long 6mm loop that I also use to attach the chalkbag around my waist. I can move the chalkbag out of my way in chimneys. The long loop can be used for Prusik, load releasable knot, abseil tat or extending the abseil plus a leash ( https://www.vimeo.com/54302232 ). I attach it around my waist using a sheet bend.
Another short 6mm loop clipped or girth hitched to my harness. I use this to autoblock the abseil or as a short prusik which I can extend with slings, if necessary. I've used it doubled over as a short draw in a pinch.
Yes, I've practiced using this to prusik but never had to use it in anger -- so far.
One which is my chalk bag cord and one which is long enough to use to escape an indirect belay with remote anchors without the need for an extra sling (as chances are I ever need to do this I'll have used my slings.