There are a lot more than 2 different sizes!
Seriously, there must be at least half a dozen different designs of postmix keg getting around. I wouldn't restrict yourself to the exact millimetre as you will no doubt get more kegs in the future and you may not have total control over their dimensions.
The shortest and widest I've got is the Rheem type (Coca-Cola) with the round screw lid and the chunky rubber base. The base is 240mm diameter and they are 560mm tall.
The tallest and slimmest I've got here is the Spartanberg type (Schweppes) with the black rubber base and handles and oval lid, at 215mm in diameter and 635mm tall.
Somewhere in the middle are a couple of Firestone types - one with stainless handles and base, at 215 diameter and 600 tall, and one with rubber base, and round continuous handles at 220 x 605mm. Both of these have racetrack lids.
This is by no means a complete list, I often see other types of kegs in people's pics that I've never seen before!
