Is he at a good size for his age?

[Reinz]

Well first off, he looks like a nice healthy Boa/BCI . He has good body form/shape and has not been over fed.

There's a significant difference between 4 ft and 5 ft. At 5 yrs, I would expect 5 ft, or maybe 5-6ft. But maybe he has been underfed some along the way. But he looks good now, so don't go power feeding him.

Enjoy him, Boas are cool snakes!