You can equip Halloween Packages in the Action slot for some reason. : r/tf2
KEY VISE-ACTION LATCH SLOT CIR - Genset Services
Walfort pantserslot | Action.com
Amazon.com: Insta360 ONE X Battery Charger Pack, Compatible with Insta360 ONE X Action Camera, LP 3-Pack Replacement Battery & Triple Slot USB Charger with Built-in TF Memory Card Reader : Electronics