I’ve used them before, can’t remember my settings but want to say it was like 800/60. You should be able to dial it in pretty easily.
The one thing I’ll say is that they looked way better when I wiped them down afterward with some alcohol. The Lasered areas pick up a little residue from burning the paint off, the alcohol picks that right up and makes them look perfect.
Oh one other thing: if you laser them too hard they will warp from the heat. If you find your cards warping, you’ll want to drop the power a bit.
You’ll get it dialed in pretty quickly, I find that 270 lpi is a good sweet spot of time versus quality.
If you ever want to step up to a more substantial metal card, the ring lord sells good anodized aluminum cards too… but while these steel ones are flexible and thin, the ring lord’s cards are practically weapons by comparison.