Rust prevention,good meterial chose,and successful exprot each month.Supporting sample provide.EPDM or ruber wahser. hex head self drilling screw with washer Meterial:steel,stainless steel Finish:zinc plated,steel Size:6#7#8#10#12#14#3.53.94.24.85.56.3 Packaging:in bulk or in boxes,then in export carton. Washer meterial:EPDM,PVC,RUBBER