Yasuhikotakia sidtjimunki, aka dwarf chain maxes out at about 2.5 inches (6 cm). I have had a dozen for many years and none of mine have reached much over 2 so far. Hoewever, Yasuhikotakia nigrolineata which looks very similar to sidthimunki when they are juveniles do get to be about 4 inches. Is it possible you have the latter?