I just tested the 15 mm one in an 8 mm thick plate of mild steel. The items has 3 cutters but only one seamed to be cutting and clogged totally when the other 2 cutters were nearly "dust free*". Cutting only a little and then cleaniong the clogged cutter made me cut down 6 mm in the plate. Then 2 (!) teeth broke off and one was stuck in the plate. The first and second picture shows where the 2 broken teeth was sitting. The third picture shows the remaning tooth.The fourth picture shows the partly finished hole containing the tooth being stck. The last Picture shoews the disassemled 15 mm item.

This seemed so good I ordered 2 sets!
But then: -Slow transport, no tracking for three weeks, and when the package finally arrives, content isn't what I ordered - only one set as per the order, then another set with only six (instead if 12) holesaws, only bigger up 'til 65 mm.

Might as well try the biggie on a 15 mm aluminum sheet - it went fantastic!
My lathe complained at 220 rpm when feeding in this 65 mm hole cutter,
but it went thru in a jiffy, with better side finish than with ordinary Starrett HSS saws of equal dia. This is due to that this cutter IS NOT mounted on a threaded mandrel like the Starretts, this one is in one piece per size: consistency guaranteed!