It is a Hex Wrench, which made of Chrome-vanadium Steel. It included 9 pieces of steel with different size. Ball ends allow up to a 25-degree entry angle to reach around obstructions Chamfered, straight ends offer a snug fit and insert smoothly into fastener head, reducing wear. Black oxide finish protects against corrosion without added plating that could chip off under high-stress contact. Long arm/short arm design offers extended reach on one end and extra leverage on the other