I bought these when putting together a starter rack on the advice of a guide for climbing a particular area of Northern California. When the set came in, I was surprised at how big these suckers were. I knew they had the potential to replace a larger (up to 3" w/#10) cams, but the size and strength of these peices really made me believe it. The wires make them a little stiff to place in every situation, but when you can make them work you know you've got a solid peice of pro. The #10 is my go to peice for a bomber anchor when I can fit it in the system. For beginning climbers, check the tech specs (sizes) on http://www.blackdiamondequipment.com/en-us/shop/climb/protection/wired-hexentricr-nut-set-no-4-10 so you know what sizes to get for your particular rack configuration. I didn't see the sizes listed on BC.com so here they are for reference:
Dimensions :
20.6/27.9 mm, 0.81/1.10 in (size 4)
23.9/33 mm, 0.94/1.30 in (size 5)
27.2/39.1 mm, 1.07/1.54 in (size 6)
33/45.7 mm, 1.30/1.80 in (size 7)
39.1/54.1 mm, 1.54/2.13 in (size 8)
47/63.7 mm, 1.85/2.51 in (size 9)
55.6/75.2 mm, 2.19/2.96 in (size 10)

As far as hexes go these are just adequate. The wire limites effective placement and the straigh sides prevent solid placement. If this is all you got, then the will work fine, but I would reach for a WC or Metolius curved hex first.

They take some getting used to but when you get them in right they are bomber and I'd MUCH rather fall on one of these than on a cam. We spent an afternoon doing single pitch routes at the crags using nothing but hexes one day. When its all you've got, you find a way to make it work.

This is the second set of BD hexes I've gone thru, and as I already knew, hexes are a valuable addition to anybody's rack. I never leave the deck without them.

This is my most used, most trusted piece of pro. I consider hexes a necessity to any climber, especially to sport climbers who want a little extra protection between run outs. In my opinion hexes are the most versatile piece of my rack.

The hexes are easy to use and fit in a wide range of cracks. They are stiff enough to aid placement but not too stiff.

Yeah, they're loud, and some people think they're obsolete... But, there's nothing as confidence inspiring as finding a big, bomber hex placement. You know it's not going anywhere.

Hexs are severely underused by the climbing community. Love the Hex! As bomber as a stopper or nut, fits in places that cams won't go well. Can't go wrong with a hex, especially with the wire.