I ordered some 1 Watt and 3 Watt LED’s from AliExpress. They were cheap, like 10 cents each. Free shipping. All good till they showed up mixed in an envelope. In regular light they are identical in appearance. Fortunately I had a small UV flashlight I had ordered. I thought it was interesting and had ordered it for $5.
It turns out that the LED’s are vastly different in appearance under UV light. This enabled me to quickly sort them. You can see the 3 Watt LED’s on the left and the 1 Watt on the right. I know the size based on the quantity I ordered.