What size jamb width is this?

I currently have a sliding patio door...switching to a French door...the doors come in 2 sizes for jamb width - 4 9/16 or 6 9/16...which one should I order? Thanks.

 

I would think it's the 4 9/16". Looks like the original door goes from about the 2 1/2" to around the 7 1/4" mark on your tape measure.

 

Any 2nd opinions before I order?

 

^ this.

 

Picture is kind of misleading - when I look at it, it more closely measures 5 1/4 (2.25 to 7.5). Why would it be in between the two jamb widths offered?

 

Going with the narrower one is safe because you can always build up for trim out.

 

The existing framing is either going to be 2 x 4 or 2 x 6. So a 2 x 4 measures around 3 and 1/2". Add a half inch of drywall and another 1/2" for sheathing and you're right around the 4 9/16" mark. The existing jam looks like it's around 4 3/4" so I'd be willing to bet it's the narrower one.