Dense are we?
"Nonspillable
Due to its completely sealed case, the OPTIMA Yellow Top battery is extremely safe and corrosion resistant. Acid can't leak or spill, making them clean, user-friendly and environmentally sound. In addition, the maintenance free sealed case design eliminates the need to add water or clean terminals."
I don't know what you have seen... But Yellow Tops are SEALED... //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
Maybe they are modded? But a stock Yellow top is SEALED...