ITEM NAME:12 pcs Metric Rubber Well Nuts Blind Fastener Wellnuts Kayak Accessories Description: Rubber nuts consist of a flanged neoprene rubber sleeve with a captive brass nut Tightening a threaded screw into the brass nut expands the insert to secure the fixing Vibration and shock resistant - dampens noise Can be used in blind holes and tubes Fits all M4 metric machine screws Specification: Material: High Quality Rubber with Brass Nut Size: M4 - Approx. 12.15 x 10.7 mm/0.48 x 0.42 inch M5 - Approx. 17 x 14 mm/0.67 x 0.55 inchColor: Black Thread: M4 M5 Package Includes: 12 Pieces Rubber Well Nuts.Can be used in blind holes and tubes. Rubber nuts consist of a flanged neoprene rubber sleeve with a captive brass nut. Tightening a threaded screw into the brass nut expands the insert to secure the fixing.