These are 304 A2 grade stainless steel small thin head countersunk rivet nuts; they are knurled to grip better against rotation with the dimensions as shown in the photo section of this listing:

• What you get: All measurements are approximate and for reference only.
• Quality: All products are of the high quality and meet the relevant international standards.
• Stock: We carry a large inventory of stock so all orders can be sent within next business day of your payment.
• Postage: All Australia domestic delivery will be delivered by Australia Post with tracking.