I tell them just as a courtesy. I think they appreciate it. Although one time, got stopped by Noblesville PD and he was real weird about it. he made me get out of the car and step like 30 ft away as he ran the serial number. All other times, they just thanked me for telling them and the proceed...
i have an a-grip on my G27 and like it a lot.
"Glock Accessories - Brooks Tactical Systems - Maker of Agrip- Gun Grips & Accessories for Glock Heckler & Koch Kahr Kel Tec Ruger 1911 MP5 Pistols Revolvers"