Funny you should mention them, took this posed photos yesterday (to compare with my 330.2mm wooden hand screw), Mine are metal and actually used them today to hold some M5 screws that I had to cut down and not melt the plastic pads on my other clamps, DOH!... on the second cut!
I have a "much bigger" plastic one, but that would also suffer melting moments,
If your first cut is too short... Take the second cut from the longer end... LBD