These are post insertion Tee Nuts that can be added anywhere along the slot of V-Slot or compatible extrusions.
Drop In Tee Nuts - Maker Store USA
Drop-In T-Nut, M6, Drop-In Style Nuts
M4 T-slot Nut 20 Series Aluminum Profile Drop in T-Nuts (20 pack
Drop In Tee Nuts Pack - OpenBuilds Part Store
M4 Drop In Tee nuts T-Nut 2020 Aluminium Extrusion Profile T-Slot
Drop in T-nuts – MakerTechStore
Differences between: T-NUT M5 vs Drop In Tee Nuts V-Slot
Drop In Tee Nut
Drop In Tee Nut
Drop In T Nut M3 M4 M5 M6 M8 Tee nuts Tee Nuts Aluminum Extrusion
X2020 Drop-In T-Nuts - M5 Thread (10 pk)