I'm a huge fan of the KNS Perma Pin (firing pin retaining pin). I grew tired of the cotter pin style, switched to KNS Perma Pin and never looked back. However, I'm not a fan of their price. The places that sell them low cost ($9 ish range) have HIGH shipping, which negates that. Places with free shipping want $12 or more/ea. I see some copies listed at $8/3 pack but are listed as 1018 steel (vs KNS tool steel). I have no knowledge of steel grades and was wondering how effective 1018 steel is compared to "tool steel"? I haven't had any issues with KNS breaking, so I'm guessing the tool steel works, and if I wasn't a cheap bastard I'd just get more of them. However, I AM a cheap bastard so I'm wondering how 1018 steel would compare?
Any feedback or info would be appreciated! Thanks.

My .02

I'm a huge fan of KNS "Anti-Walk" pins.

But I've never tried their firing pin retainer, I HAVE purchased a similar pin from DPMS.

It appears that KNS has "nubs" on the split section to help retain the pin in place, the DPMS doesn't.

There is NO "spring tension" on the DPMS pin nor are there any "nubs", turn the carrier sideways and the pin will fall out.

The DPMS units are CRAP!!!

But even if there is no tension to retain the DPMS ones, doesn't the receiver hold them in?

Correct. But the DPMS are junk. The steel is very soft.

I'm updating this thread because I tried the ebay $7/3 perma pin knockoff's and they work just fine. Granted, I've only put about 500 rounds through with it, but it's holding up just fine (easy in/out, does not fall out, holds just fine). I'm ordering more. I'm not sure why others are adamant about using the silly cotter pin style, but I'm not and won't. Stoner designed this part as a dedicated pin, and that's what it should be (IMHO). The KNS Perma Pins work great, and so do these FAR cheaper ebay versions. I'll be ordering more of these little buggers.
ETA: these are the pins I'm using now:
http://www.ebay.com/itm/223-5-56-firing-pin-retaining-pin-223-5-56/390660618724?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32222%26meid%3D09ffd1a0d1494c0680bafa95d20fd066%26pid%3D100005%26rk%3D2%26rkt%3D6%26mehot%3Dpp%26sd%3D310889042453&rt=nc