Can someone confirm that this is a true B. Kahlenbergi?

Definitely female.

@EtienneN Yep, which is nice, but I wanted to know if it's a true Kahlenbergi as they are identical color-wise to Vagans

@TheDarkAbyss You’ll have to see if someone can confirm species for you with the shape of the spermathecae since that should be the deciding factor.

angustum molt

@macaridonte I think that's a bit of a stretch, comparing your angustum spermatheca to this one. It helps, though!

http://tarantulas.su/en/sexing

to many red rumps visually identical that can only be differentiated by the spermathecae

The uterus externus of mine has a triangle shape while yours is the usual rectangle