Do .12 gram BBs look different than .20 gram BBs?

Is there a way to tell the difference from a .12 gram BB to a .20 gram BB? I bought an airsoft pistol and it came with a pack of BBs that didn't have anything on it saying the grams, and I also bought a pack of off-brand BBs that didn't have the weight on it either. Is there a way to tell by looks alone?