Hard to say from the pics, but it is definitely a common. One thing to remember with "common plecos", is that the term 'common' stands for a basic coloration, that can be found in many species and genus. Count the hard rays on the dorsal. There are some species of common that stay very small. I have one Pterygoplichthys species, that I have had for ~5 years, and he is only a mere 6" SL. I have had others hit the 16" mark in less than a year.