Specifications:With complete specifications and models, you can buy adapters of any specification according to your needs.The surface is treated with carbon black phosphate, which is beautiful and generous, and soaked in anti-rust oil, which can prevent rust.Industrial grade chromium molybdenum steel is formed without splicing, strong impact resistance, high hardness, and good toughness. Item Name: AdapterMaterial: Chrome Molybdenum SteelFeatures: Durable, Complete Specifications and Models, Easy to UseProduct Size:1: Product Name: 3/8 to 1/4: Square Hole Diameter: Concave 9.5mm/0.37, Square Head Diameter: Convex 6.3mm/0.25 (Approx.)2: Product Name: 1/4 to 3/8: Square Hole Diameter: Concave 6.3mm/0.25, Square Head Diameter: Convex 9.5mm/0.37 (Approx.)3: Product Name: 3/8 to 1/2: Square Hole Diameter: Concave 9.5mm/0.37, Square Head Diameter: Convex 12.5mm/0.49 (Approx.)4: Product Name: 1/2 to 3/8: Square Hole Diameter: Concave 12.5mm/0.49, Square Head Diameter: Convex 9.5mm/0.37 (Approx.)5: Product Name: 1/2 to 3/4: Square Hole Diameter: Concave 12.5mm/0.49, Square Head Diameter: Convex 19mm/0.75 (Approx.)6: Product Name: 3/4 to 1/2: Square Hole Diameter: Concave 19mm/0.75, Square Head Diameter: Convex 12.5mm/0.49 (Approx.)7: Product Name: 3/4 to 1: Square Hole Diameter: Concave 19mm/0.75, Square Head Diameter: Convex 25.4mm/1 (Approx.)8: Product Name: 1 to 3/4: Square Hole Diameter: Concave 25.4mm/1, Square Head Diameter: Convex 19mm/0.75 (Approx.) Notes:Due to the light and screen setting difference, the items color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement. Package Includes:1 x Adapter