Y-Back String Tank Tops from Powerhouse Gym. These men's string tank tops were exclusively made for Best Form Fitness Gear and are only available here! The shoulder straps on this stringer tank top are narrow, but sewn so they won't roll-up. The Powerhouse Gym logo is screen-printed across the front and these muscle tank tops are made from 100% cotton. The y-back design with low-cut size allows for a fuller range of motion during the most intense workout and also makes these tanktops comfortable to wear in hot gym environments.