4ft LED shop lights replace 2-lamp T8 fluorescent fixtures at 38-60 watts and 4,000-7,000 lumens. 8ft LED shop lights replace single-pin T8/T12 fluorescent strips at 65-120 watts and 8,000-20,000 lumens. Choose 4ft for ceilings 8-14ft (offices, shops, retail) and 8ft for ceilings 10-20ft (warehouses, production floors, parking garages).