What toilet is that for? I have a Cadet 3 1.6gpf which came with their universal bowl which can also use their 1.25gpf tank. Then there's the rough in size, 10, 12 or 14". Each uses a different size tank. If you had a 12" rough in, if available, you could use a 10" tank to leave space behind it to the wall but less space on sides and higher also.