These are TO-220 heat sinks, as you would use with a voltage regulator. The black ones are from Mouser, and cost CAD$1.38 each. The silvery ones are from AliExpress, and come with thermal pads, screws, and little white insulators, and cost me CAD$3.00 for ten, or CAD$0.30 each. You tell me which is the better deal.