I have an identical pair in my "Colt Stocks" drawer-marked "Franzite",which I think these are. Doesn't matter,as Dant is right about the warping,especially when you tighten the screw!
Franzite stocks for the Colt E/I Frame tend to be habitually "short" for a proper fit,leaving a space at the top or bottom. Some of the more "honest/informed" eBay sellers will point this out. Franzite plastic stocks for the New Service,tend to be "short" also,but not as bad as the E frame.(I think they used a very early 1892 Army/navy for a "model"!!)..
Fitz tended to make more of a thumb rest style of plastic target grip,sometimes called "Ten-O-Grip".or "Gunfighter Grips(old Numrich Arms catalogs have them pictured)
Franzite,as dant said,covered "all the bases",and their non\magna S&W grips fit and look nice.
Murad made the plastic grips called "pointer pups",and the fake stag versions of these were factory issue on most Great Western Arms SAA clones,1954-1960. These fake stags are very popular with "cowboy shooters",and have seen them go for $25.00 on eBay: I got a bunch in my "Great Western Drawer".
Generally,Jay Scott was considered the elite of the mass produced after market grips,but were priced higher.