I know it's a hen but what breed?

[Michael OShay]

So can you tell if this is a RIR or a Red Sex Link pullet?
She does have white underfeathers...

She looks in your photo like a Rhode Island Red hen. I don't see any white underfluff in your photo (granted it's not a profile or rear shot), but normally the white underfluff is real obvious in a Red Sex Link and typically extends into the tail feathers as well. Also, while I can't see the tail well in your pic, there are probably some black tail feathers (instead of white) in her tail which Red Sex Link hens never have. I have posted some pics below illustrating the difference between RIR hens and RSL hens.
Rhode Island Red hens (below on right) Red Sex Link hens (below on left)

Googled from http://4.bp.blogspot.com/-nJuG7MqIo...ZY8aBVXgo/s1600/rhode-island-red-chickens.jpg Googled from http://www.cacklehatchery.com/images/runner_up_0027-001.jpg

 

[Michael OShay]

The pictures didn't come out side-by-side like I was expecting, but the Rhode Island Reds are in the top photo and the Red Sex Links are in the bottom photo.

Googled from http://4.bp.blogspot.com/-nJuG7MqIo...ZY8aBVXgo/s1600/rhode-island-red-chickens.jpg Googled from http://www.cacklehatchery.com/images/runner_up_0027-001.jpg

 

[AnnieSantiago]

Ok. Thanks.
Yes, She is a Rhode Island Red.

 

[Chris09]

So can you tell if this is a RIR or a Red Sex Link pullet?
She does have white underfeathers...

She's a production red, a Rhode Island Red should not have the lacing she has. To me I think she may have some Brown Leghorn in her, that would account for the lacing in her breast.
A lot of hatcheries will cross a Dark Brown Leghorn with a production type Rhode Island Red or production red to darken the offspring up and try to get the offspring more correct in color but the outcome is lacing and uneven color.

 

[Michael OShay]

She's a production red, a Rhode Island Red should not have the lacing she has. To me I think she may have some Brown Leghorn in her, that would account for the lacing in her breast.
A lot of hatcheries will cross a Dark Brown Leghorn with a production type Rhode Island Red or production red to darken the offspring up and try to get the offspring more correct in color but the outcome is lacing and uneven color.

Chris09 is technically correct. I didn't get into the Rhode Island Red/Production Red distinctions because hatcheries often market their Production Reds as Rhode Island Reds (you likely bought yours as an RIR) and my main point was to differentiate between Red Sex Links (which are red X silver hybrids) and true red gene birds (whether RIR, NHR, or Production Red) that will reproduce as such.

 

[pineapple416]

She looks like a red sex link hen to me

 

[Wyandottes7]

She's a Production Red.

 

[BantamLover21]

CharterChick, your bird is a Red Sex-link pullet.

AnnieSantiago, your hen is a Rhode Island Red/Production Red. A Red Sex-link would have more white on the surface.

 

[CharterChick]

Thank you all!

 

[Michael OShay]

Thank you all!

You're welcome.