Are the SWD steel DIAS considered to be good quality & do they require any shims typically to get running right? Really any info on them would be much appreciated thanks

The most critical thing when purchasing an "SWD" RDIAS is that the serial number does not start with "AC" i.e AC315.  

A real SWD RDIAS serial will start with "AS" and the following number should be no more than roughly 100.

Any SWD manufactured RDIAS that has an "AC" prefix serial number is illegal at worst or has a highly damaged legal pedigree at best as they were made from SWD Registered Lightning Links.  In some cases bits of a cut up Lighting Link were welded to a new DIAS body (see below) or the RLL serial number was just transferred from to a new DIAS and the old RLL was destroyed.

It was a bit of a cottage industry 10+ years ago with some sellers to make more money by taking a lower value lighting link and magically transforming it into a DIAS for double the profit.





As to functionality they are all pretty simple.  There is no standard DIAS shape/profile and there is no 100% standard semi-auto AR15 lower pocket either as the depth of the shelves vary as do the sidewall interior cuts, the same goes for the rear lug on uppers as the depth front to back can also vary.

So a specific RDIAS may fit snug in one lower/upper combination and need shimming in another.

Thank you for that information. The one I bought doesn't have an AC or AS prefix just an A prefixed serial number.

EDIT: it looked like A5 XX on the piece, but is indeed AS on the paperwork.