Not speed nuts, more like these: https://www.anzor.co.nz/washers/internal-tooth-lock-washers Only with thinner metal on the teeth and the teeth are wider too.

[edit] - bless google image search, even with inaccurate search terms it can be rather useful :3 As it appears these are very much the same as the ones on the axles: https://www.ubuy.co.id/en/product/R9C66IW-oiiki-200pcs-m2-m2-5-m3-m4-m5-internal-tooth-starlock-washers-quick-speed-locking-washers-push-on-sp