It seems like this product is a hit or miss. Some reviews say it fits perfectly, some say it does not. I belong to the 2nd group. I tried to put it on 55-250 IS lens - for storing it on the hood, it fits perfectly, screws on and off really smoothly. To put it on for taking pictures is a different story - one of the blades seems to be a hair thicker than the rest. This makes it REALLY hard to put it on, I'm afraid I'm going to damage the lens, if I keep putting it on. It only goes on about a quarter of a turn... But it stays on securely then. But, it's a bit bigger in diameter than the lens, so, you can see daylight between the lens and the hood. I guess I'm going to have to shave that blade a little bit. If that won't work I'll throw it away. Also, I expected it to be a little sturdier. It's a shame, because it's a great looking hood for a great price. Oh, and shame on Canon for price gouging on their lens hoods! There's no way a small piece of plastic should cost that much...UPDATE - after I shaved the blades it fits just fine.