For the ladies...
any t-shirt can work...but these are a little better cut.
Bella Ladies Raglan 3/4 Sleeve Tee 100% supersoft high cotton 1 x 1 rib 5.8 oz. 3/8" bound-on self-trim neck (matches sleeve color), 3/4 raglan sleeves. Double-needle bottom hem, tapered side-seamed body.
raglan 3/4 sleeve in black & white
raglan 3/4 sleeve in red & black