I believe the little plastic cup is intended to keep odds and ends accounted for when doing maintenance. Which is very odd, since no part of the gun save the locking block will fit in that 'lil cup. I use mine as a thumbtack holder on my desk.
My dad carried a Beretta 96 as a cop for about ten years, and he was amazed when he could do much more rapid followup shots with a gun about 1/3 lighter.
Beretta PX4; 92FS; 92S; 8040G | Sig Sauer SP2022; P6 | Glock G19 Gen4; G23 Gen3| Colt Python 4"; 1968 Detective Special 2"| Smith & Wesson M642-1 | Ruger LCP; 10/22 | Daniel Defense M4V1 | Remington 870 | Alpine M1 Carbine | Steyr M1895 |1943 Izhevsk Mosin M91/30 | Walther PPS