Invisible Floating Shelf Brackets, 4" (100mm), Hidden Blind Supports for Concealed Shelves, Pack of 4Specifications:Material: IronShaft Diameter: 10mm / 0.39"Size(Approx.):100 x 70 x 14mm / 3.94" x 2.76" x 0.55"(L*W*H)Mounting Hole Size: 11 x 6mm / 0.43" x 0.24" (L*W).Mounting Hole Distance: 42mm / 1.65"Package Content: 4 Pcs x Concealed BracketINSTALLATION GUIDETools:1.Every bracket will need screws x2, anchorsx2, washer x2. (All are not included)2.You need to have Level, Drill, Electric Screwdriver, Hammer. (You may need drill press if the shelf is DIY)STEP:1.Drill holes on wall - You should use level to mark cross on the wall to make sure you drill the holes in the right place.2.Install the bracket - You can use washers to help the bracket install tightly. Electric screwdriver is highly recommended.3.