I have read on several different sites, this Kimber part was one of several replacement options for the Colt Defender RSA.
EGW also has one listed for replacement although a different construction.
www.egwguns.com
As far as any reports on “using/shooting” I haven’t really searched or found anything positive or negative.
On my Defender, while reassembling, I just hold the RSA with my thumb as I install the slide. Functions normally.
For me “No biggie”.
EGW also has one listed for replacement although a different construction.
Search results for: 'Colt Defender RSA replacement'

On my Defender, while reassembling, I just hold the RSA with my thumb as I install the slide. Functions normally.
For me “No biggie”.