EPC has two "tabs" flanking the cutout for the port cover spring. These tabs allow the EPC to rest on the upper at a greater angle when it's in the down/open position, which provides more space between the port cover and lower receiver. Their job is to better allow the user's finger to get underneath the port cover when he wishes to swing it up/close.
Another feature is a shallow circular depression on the side of the EPC to provide texture tactile feedback to the user's finger when he's closing the EPC. A flat surface provides nothing to the user to differentiate one surface from another, it also provides no traction. A shallow circular depression on the left side of the EPC does both. FCD incorporates flat surfaces with care as they have their uses . In this case, EPC's exterior surface is treated as a control surface, where a flat surface rarely makes sense.
EPC is compatible with TDP spec upper receivers.
Construction and coating: billet, type III anodized.
Proudly designed and made in the USA.
Initial closing and opening of EPC may be stiff, this is normal, and will become easier with 2 or 3 closing/opening cycles.