The everyday option — a single compression undershirt at the price point where it is worth trying before committing to a multipack.
What it does
Firm compression through the chest and stomach so a shirt sits flat. Worn as a base layer, invisible under clothing.
Sizing
Runs tight by design. Between sizes, take the larger one.
If it works for you
The 3-pack and 5-pack on this site work out cheaper per shirt, and you will want more than one — compression is worn daily or not at all.