XM177/CAR15/M4A1/M4A2 collapsible stock mil-spec and aftermarket examples, similar but different

SHOW AND TELL: XM177/CAR-15/M4-A1/M4-A2 type collapsible stocks mil-spec and aftermarket examples, similar but different.
Stock examples from Brownells, Colt, Spikes Tactical, and other.
Also:
Aero Precision
AR15/AR10 Carbine Buffer Tube
Midwest Industries
QD Rear Sling Adapter for 4-position CAR STOCK
QD Rear Sling Adapter for 6-position CAR/M4 Stock
HK style hook Sling Adapter for 6-position CAR/M4 Stock
B&T Industries
BT12-QK: Standard Height Accu-Shot® Precision Rail Monopod