Flat head cap screws, 12mm female thread diameter, 24mm total height.
A rivet nut fastener is a tubular rivet with internal threads.
Once installed, they are permanently attached to the mating material, allowing the associated nut to be removed in service without the risk of the fastener becoming dislodged.
 

• Thread Size: 12mm/0.47''(D); Product Name: Rivet Nut
• Material: Carbon Steel, Yellow Zinc Plated; Weight: 214g
• Package Content: 20pcs x Rivet Nut; Main Color: Bronze Tone
• Height: 24mm/0.95''; Flange Size: 18 x 2mm/0.71'' x 0.08''(D*T)
• Application Hole Size: 13mm/0.51''(D); Body Dia.: 14.9mm/0.59''

Thread Size: 12mm/0.47''(D); Product Name: Rivet Nutuxcell