What is inside this wall?

Question

I live in a condo, and there is a hole on one of the wall, and it has "A B P, L - L" on top of the hole, and inside, it looks like a tube for water? it doesn't looks like a cable or a phone line.

i don't know what it is, can someone tell me?

Answer 1

Maybe a overflow line for the A/C or water heater, does it sit over a tub or sink?