Washers are normally used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened. Intended for the general use under the head of a bolt or nut in order to provide a smooth-bearing surface. Product Name: Flat Washer; Material: 304 Stainless Steel; Weight: 146g; Package Content: 500(+/-2%)pcs x Flat Washer; Main Color: Silver Tone; Inner Dia: 4mm/ 0.16"; Outer Dia: 9mm/ 0.35"; Thickness: 0.8mm/ 0.03"