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 .40 S&W - Beretta 92FS 9x19 Para - Rock Island Armory GI 1911 .45 ACP - Colt 1968 Detective Special .38 Spc. - Ruger LCP .380 ACP - Daniel Defense M4V1 Carbine 5.56x45 - Alpine Industries M1 Carbine .30 - Steyr-Mannlicher M1895 8x56 - Ruger 10/22 .22LR - Remington 870 Express Tactical 12GA - 1943 Izhevsk Mosin-Nagant M91/30 7.62x54R