Made Iron plating.The carbon steel material features strength,wear resistance and resistance in bad environment like high temperature,cold weather,and high humidity areas. and nickel plated guarantees protection against environmental damage and rust.Superior rust resistance and oxidation resistance ensures their durability. EASY TO INSTALL:cage nuts and screws accord with standardized metric system.And the average error is less than 0.1mm.The screw thread is quite ,clean and accurate without burr.The accurate size makes your installment or repair easier.They fit your cages well, Package includes:meet your different needs.It is a good choice for both professional and amateur.These multifunctional bolts and nuts are your must-have tools. Widely Applications:Cage nuts and screws are universally compatible with all square-holed racks.nuts and screws are great for mounting your rack server cabinets,server shelves,A/V device enclosures and more. High quality cabinet cage nuts and screws Size:M6 x 20 Fit all square hole racks server rack or cabinet Color:silver material:metal Package Contents: 50* M6 cage nut 50* M6*20mm screw Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.