You are right Redsy. Square D makes a QOU unit mount miniature breaker as low as 10 amps in 120/240 volts 1,2,3poles and 277 volts 1pole.
Art. 240-6 of the 1999 NEC list only as low as 15 amps, but the next sentence says non-standard fuses and inverse time breakers shall be permitted.
