The case is configured to hold the heli w out dissassembly,its over kill for a lot of folks,but it handles the 90,000 miles a year I cover both on the ground and in the air.(w no damage to the heli)
To come up w a size,measure from the tip of the canopy to the furthest point on the tail,and from the bottom of the skids to the top of the rotorhead and add an inch,also add an inch lengthwise
Then measure from the outside of one skid to the outside of the other.