I recommend sizes 2-5 over the equivalent size BD Stoppers, especially for shallow placements. These have a good taper and typically fit with excellent surface contact. The steel-copper alloy is hard enough that it won't shear when whipped on in hard stone. When the placement is too flared for these, try DMM HB Brass Offsets

These guys are not nearly as good as the DMM brass offsets. In terms of micro nuts, the dmm's are WAY better

I bought these to supplement my set of anodized aluminum stoppers (down to 3), thinking that they would protect MUCH smaller cracks than my aluminum stoppers would. This has proven to be somewhat of a misconception, although the Micro stoppers fit shallower placements better than the aluminum ones, the #3 Micro fits cracks of a very similar width as the #3 alu. stopper,(see photo) likewise for the other sizes.

So why would you buy these (for free climbing) if you already have the aluminum set? First off, I have found that Micros seat better than alu in the same placements. This means that they are less likely to get wiggled out as you pass by, which is great, because if you're placing gear this small, its likely your only option for pro, so it NEEDS to stick. Secondly, because of the narrower head, Micros fit in shallower thin cracks that Alu stoppers would be unstable in. Third, Because of the lack of a cable crimp (the cables ends are permanently fixed in the stopper head), Micros are lighter and rack cleaner than equivalent Alu Stoppers.

For free climbing, these are really only necessary on a minority of routes, most of them 5.10 and harder. That said, these hardly take up any space or weight on your rack, and when you place one of these, there's a good chance that its the only thing that fits.

For free climbing, I'd recommend sizes 3,4, and 5. The 6 is hardly micro, and 1 and 2 probably wouldn't hold a fall. Also, 3+4+5 combined weigh about as much as a Neutrino, so they won't inconvenience you if yo don't use them on a pitch, but you will be STOKED if its all that's available and you brought them along.

These are much stronger for the size than regular aluminum nuts. They are pretty tough and set nicely. You should really only use the steel stoppers in hard rock like granite, use brass ones on stuff like sandstone.

The wires can bend at the joint pretty easy, that is my only gripe but it happens, what ever...

Oh B.D. Micro stoppers infused with brass
You are nothing short of Totally Kick Ass
Your always with me when I'm out on a caper
Your there for me when the cracks are thin as a paper
Some people shiver but my eyes just gleam
When ahead lies nothing but a miniscule seam
I have no reason to fear
When I've got you hear
Yes right on my gear loop you wait in a set
Oh BD Micros you are a sure fire bet
Sometimes I'll even resort to the two and the one
but I try not to whip because it wouldn't be fun
But when I whittle in a good number three
I know it is bomber and this gives me glee
How many sad stories end with and then it got thin
But I didn't have micros and so couldn't win
I don't ever want to sing that sad lonesome tune
So I always have micros when I shoot for the moon
You've saved me from abrasions, sprains and even broken legs
That's why to you Micros I owe oh so much thanks.
Thank you Micros thank you.... I love you you are my bestest friend
My love for you knows no bounds, borders nor even an end.
So one more time micros get on my rack
And lets go sketch out up a micro thin crack.

The are some great nuts! Very light and although you want your placements to be perfect with micros, these are easy enough to place. I took a few 10 ft whips on a #4 and the piece was still in tact after, no kinks. They are so light, it's worth carrying them just in case.

Took a whippet on the silver, held like a champ, little deformation in the wire due to placement, but fantastic easy to place pro. I like how one of the wide sides flare for placements in little seams

I agree with Grove, I hate falling on these, but when a whipper is coming, I take at least a little reassurance in these things. Also they are way more durable than any other micro I have used. If needed you can lightly hammer them into a crack and they still remain usable afterward.

These little wires are burly, they stand up to more beating then standard brass, and the taper makes them fit into funky cracks nicely.

So it is not my favorite activity, falling on Micro's. But if I have to these are the ones that I choose. Never let me down unless I make a bad placement. Extremely durable also, made to take a beating.