Pleco type?

Hi!
Could you tell me what type of Pleco this is? is it a common Pleco that grows massive?
Thank you
Tracey

Positively identifying young plecs can be difficult as so many of them look alike when they're small, but looking at the finnage I'm 90% certain that you have a sailfin/gibbiceps plec and yes, they do grow big; around 18" or perhaps 2 ft.