Nylon. It's not just for panty hose anymore. It's for inexpensive slings that outperform their high-tensile cousins, for reasons we'll get into shortly. Metolius gives us a decent cheapo with a few rough edges.
Metolius made a workman's sling here, rated at 22kn. It's 18mm wide with pinstriping down the center, just like the decals you put on your crappy old pickup truck when you were a teenager. Don't lie, someone saw you. The rough edges are on the ends, where at least on the one I got it looks like they were cut by someone operating a hot knife under the influence. The ends stick out half an inch from the bar tacking, which won't affect much but is annoying from a purely anal-retentive perspective. Which is the only perspective we know around these parts.
Where the 48 incher weighs 3oz, some of they fancy high-tensile sewn runners weigh in at a mere 1 oz. OK, sure, that's 2 oz. apiece and I like to count grams as much as the next weenie. But picture this: you're clipped in to a piece of pro with your webbing and for some reason you're above the pro, you slip and you fall. Chances are the nylon webbing will hold. The high-tensile dyneema/spectra/kevlar sling will snap, because it can't stretch even the teensiest bit. That means the peak load is much higher and it fails. Check out the current gear guide issue of Rock and Ice Magazine. They confirm tests by others that show this nifty little fact, and remember: knotting high-tensile slings steadily reduces their strength while nylon can be knotted and unknotted forever with minimal loss of strength.
Winter will be here soon, when young climbers thoughts turn to frozen waterfalls and alpine ascents. Rock climbers, however, will be screwed. That is, unless they have access to an indoor climbing wall, which is where Metolius Mega Pack climbing holds come into the picture.
Most of the time when someone comes up with a device that is just a specialized version of something you can rig yourself from stuff you already own, it's just not worth paying for. This is not that.