SIG SIG556 to SIG551-A1 Swiss Transformation Kit
SIG Sauer has a limited number of complete SIG551-A1 lowers, including stock and magazine, which can be used to convert a SIG556 to a SIG551-A1.
Only 250 kits are available and they are only taking phone orders. Call (866) 619-1128 or (603) 418-8102.
[ Many thanks to Matthew for the tip. ]

They are 369 bucks, well worth it IMO to turn my SBR’d 556 pistol into a more faithful clone of the 552! Considering that people were up until recently paying similar to that for the swiss stocks alone, I don’t think that its a bad price at all.
The real question is how much money? I bet its a arm and leg.
Trigger guard still doesn’t match the Swiss version.
It’s good looking, but you would have to be part Swiss to really appreciate the 551 differences over the 556 imo.
Yea, and want to spend a lot more on mags.
This must be aimed at those who shoot HK pistols and SCAR 17s. You see we just have find a way to spend more money on magazines.