Only suitable for light plastic and light wood. Don't bother with metal unless it looks like a thin alloy. As if it weren't obvious, you get what you pay for. I would give them 1 if the price wasn't so good. Just don't expect anything anymore. They are great for emergencies. The case is better than the tool itself lol. They are extremely thin and the TPI (Teeth Caress an Inch) is too aggressive and deep for such thin blades that they just burn out. Again, the price is cheap enough to be expected. Also wear rubber gloves. They are immersed in oil to prevent rusting. But damn. Next time you need to change the oil in your car, just hang this cover up :P