Levi is long and lean, so a lot of store-bought clothing doesn't fit him well. XS is usually too short (like a belly shirt...and he's just too many for that). Smalls usually do well for length, but they can sometimes be really baggy. I also despise when boy clothes are too long on the underside and they get peed on.
I also prefer for shirts to have sleeves. Another little preference is that I like for sweaters/jackets/coats to have slits for the D-rings of his harness, rather than an attached D-ring or nothing at all.