These are absolutely necesary for dropping the knee, ESPECIALLY if you're heading off-piste in deep snow. Initially I thought that the Arc'teryx price was too much compared to the BD knee pads (of which I'm not really a big fan due to their consistently varying movement), but the simple design and quality product have won me over time and time again. I have had three times in which I was tree skiing in some deep snow and the trailing ski had gotten buried under a fallen tree while the leading ski didn't. If I wasn't wearing these knee pads then it would have been a lot more than $60 to replace a shattered knee cap or fix a broken leg.
I never go out without these on now. They'll durable, easy to adjust (even through your pants), and are not bulky at all. Get these and set your mind (and knees) at ease.
This is really some of the best knee pads out there