Strider Harness is a common Artifact — Equipment card from Rivals of Ixalan (RIX), collector number 183. Current market price: $0.07 (foil $0.27), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+1 and has haste. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)