>>8999011>3.8Only old-school 1/18 figures, like old GI Joes and Star Wars from the 80s, are 3.75". Modern 1/18, like Acid Rain, is generally 4". So your figures may not fit so well unless there's enough space to contort them a bit.
I would just play it safe and get one like this, with removable dividers. Then you can resize if you need a little more room, make smaller compartments for weapons, etc.