Trachycephalus resinifictrix - Milk Amazon frogs grows 3 to 3.5 in. SVL, males being the smaller. They are arboreal so taller enclosures are required. Either a 40 gal. vertically converted aquarium or a 24x18x24 in. ExoTerra as a minimum should work out OK for couple or trio.

These frogs are sometimes available as froglets and as such are very delicate. Would keep those in a quarantine like environment with damp paper towels as substrate until they are strong regular eaters.

They are very tolerant of temperature; but mid to high 70's during day with a drop to 70F at night sets them fine. For humidity would target between 65-70%. As long as those parameters are met; you can pretty much set enclosure as for any other tree frog, more info about that in here: Frog Forum - Red-Eyed Leaf Frog/Red Eyed Tree Frog Care - Agalychnis callidryas or look in the Tree Frog or Vivarium sections. Good luck !