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the MS-38 / MS-39 is kinda round and bended round also
it is how you see it in your imagination 😮 😮
but your idea of round is probably the OA-55 style and the answer is given here above
😉
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The MS tanks are made out of round tubing but resemble a sausage ring more than an juice can like the OA tank does and hence are referred to as ‘sausage tanks’.