Metal bronze color rivet, about 8mm & 6mm height. Check out this link if you need the installation tools for better result, otherwise you can just use normal hammer to install.
6mm: Rm4.00 for 1 pack (24 sets)
8mm: Rm4.00 for 1 pack (20 sets) - sold out
Rm10 for 3 packs (can mix, price will be adjusted after order received)