The Samsung Galaxy S6 and Galaxy S6 do not come with a microSD card slot, instead you are limited to the built in storage, although it looks like the Samsung Galaxy S6 Active may come with one.
According to information published on Reddit, the new Samsung Galaxy S6 Active will have a microSD card slot, but will lose some of the features of the S6.
The Galaxy S6 Active will apparently ditch the fingerprint sensor and also the heart rate monitor and it may come with a different camera than the Galaxy S6.
The handset is expected to come with the same 5.1 inch display with a Quad HD resolution of 2560 x 1440 pixels and it will also apparently come with an eight core Samsung Exynos 7420 processor and 3GB of RAM.
The device is rumored to feature a larger 3500 mAh battery than the Galaxy S6 and S6 Edge and it will also be waterproof and dust proof and feature a more rugged enclosure.
According to the details posted, the handset is still under development, so there are no details on when the new Samsung Galaxy S6 active will launch.
Source Reddit, Phandroid