I have the M/M and wear a 16.5 34/35 shirt and these fit me well and is tight which is perfect for an undershirt. I have had M and they are too short

I went ahead and bought 30 of them I like them so much!

They have held up well over the last year and I use a crystal stick antiperspirant so the armpits have no yellowing
<a data-hook="product-link-linked" class="a-link-normal" href="/Thai-Deodorants-Thai-Natural-Crystal-Deodorant-Push-Up-Stick-2-125-oz/dp/B000S83JR0/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Thai Deodorants Thai Natural Crystal Deodorant Push-Up Stick 2.125 oz</a>