Sparring Collar is a common Artifact — Equipment card from Fifth Dawn (5DN), collector number 154. Current market price: $0.21 (foil $0.55), TCGplayer market prices via Scryfall.
Equipped creature has first strike. {R}{R}: Attach this Equipment to target creature you control. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)