Steel side support arms for maximum strength, following the bike&';s body lines to keep it tight and slim. Top plate is aluminum to keep weight low, drilled and threaded with several M6 and M8 holes in various locations to mount accessories. Outfitted with tie-down slots to keep strapped loads from sliding and shifting. Mounting hardware included. All components are black hammercoat finished for long life and durability. Supports up to 25 lbs.