Its just a simple box made from scraps lay about my garage, It was pure luck that all the bits fitted in, in the end drink involved. whilst trying to make it as small as possible, As I was building it I too thought it was bigger. Originally the parts were arranged differently more spread out not as tightly packed.... a happy accident, at one point I thought I had made it too small. Funny story drink involved again the final arrangement parts fit in perfectly box complete... after first time using it when packing away couldn't get the sliding lid to shut.... before I used it it had been packed & unpacked a dozen times & there had always been 1/8th" clearance above that cup, I tried for ages same lay out...in out back in, long story short it turns out one cup is smaller by 1/8th" of an inch than the other 2 height wise who would have thought? the same cup I had obviously quite by chance done all my measuring with, took me ages to puzzle it out... any way thanks guys...