Starter question

Ok, today my starter took a poop. it had been acting real weak, and finally i turned the key and nothing happened. the tap worked for a few starts, my dad offered to buy me one so i went to advanced and got a new one with a lifetime warrenty. my question is my OEM starter on the bottom had a plastic like plug in the hole that faces the ground on the end of the starter near the front of engine. the new one came with a rubber tube on the end of it. enlighten me to the purpose of this and if it matters. thank you. btw it works great, turns over nice and strong, just wondering about that one peice.

Vent? Maybe.

Got mine at advance too about 2 years ago, still strong. But just replaced my wires as well, went to a 2 gauge for less resistance and more amperage availability. Mine had that tube as well, I'm thinking to drain any water or moisture out. Wait, yeah that's my final!