ESF (End plate, Sling adapter, FCD) was first introduced in 2018 in two versions: ESF-L (7075, Type III anodized), and ESF-H (4140, DLC coated), both are the 3 socket variant, with a QD socket on both sides, and a rear socket for QD swivels.
ESF-L (7075) was very popular, but it was aluminum and didn't accept staking. After one year of production, the decision was made to go to all steel. ESF-L was discontinued, ESF-H was supplemented by the single QD socket variant, ESF-H1. Both ESF-H and ESF-H1 are machined in 4140, either DLC or Cerakoted.
In 2024, ESF-E (eyelet) was introduced. ESF-E features a robust eyelet for HK style hook, Blue Force Gear's ULoop, or paracord. Along with MFH (MLOK Fixed loop, Heavy, a collaboration with Rooftop Defense), and RSF-H (Rail mounted, Sling loop, Fixed, Heavy for 1913 rails), ESF-E is a part of the effort to offer sling mounting solutions that are not wholly relying on QD swivels.
MFH:
RSF, H:
QD has it uses, we don't believe it's applicable for every submachine gun or rifle. Fixed loop and eyelet mounts don't need a QD swivel, and usually results in a slimmer profile package.
All of ESF variants are machined in 4140, but we don't heat treat or nitride them, hardening the end plate would make them difficult to stake. The billet machine and coating (DLC or Cerakote) construction method makes ESFs some of the most expensive end plates in the space.
Below picture shows ESF's evolution.