This is a version of @Gemeneye_212233's Slide Replacement/Stock Attachment for the Mayfly (Nerf Maverick flywheel conversion) with Fidlock stud attachment locations on the left hand side of the slide.
The studs are 60mm apart, and it is designed to use the medium size Fidlock studs/screws available from Out of Darts. While the conceptual usage is similar to the Hold-ster also available from them, it has not been tested for compatibility.
https://outofdarts.com/products/fidlock-snap-male-bolt-magnet-medium?variant=39742098440234
The studs are mounted at the same angle as the magwell is on the blaster, allowing the magazine to lie parallel to the leg when using a dropleg style holster. The holes are un-threaded so for now just use either a tap or an M5 bolt to cut threads into the model after printing).
The author remixed this model.
Mounting points for medium size Fidlock bolts have been added to the left hand side of the slide, allowing it to be used as an attachment point for holster compatible studs, similar to the Hold-ster.