Oh ok, how big do these things grow?The most common use for the initials "MTS" is "Multiple Tank Syndrome", a disorder which affects a large percentage of serious fish owners. It starts with only 1 tank and night sweats and continuous hand wringing and ends with at least 5 tanks in your house full of fish.
The other "MTS" is "Malaysian Trumpet Snails" which is the topic of this thread. These are small livebearing snails with a trumpet/spiral like shell.