Basic Card Holder (UK)

This is a design I made using onshape just to learn the process of designing CAD files. It's my first ever creation so don't judge me too harshly. It's a very simple card holder for UK business cards but I made the internal dimensions 3.5" so in theory it should be exactly the size for US cards too, if not just increase the size by a small %. I printed without supports and needed to sand the upper bridge so supports are recommended.