Ambi safety selector
I recommend the selector from Battle Arms Development over all other selectors. Model BAD-CASS is the one I've had. It functions with every trigger I've used (most importantly, the Hiperfire ECL), and it is the most comfortable with just the right tension. I also love having a 45 degree selector. They have 90 degree options. It is fully modular, so you can choose the length of the levers. I use the standard length on my thumb side, and the shorter one on my knuckle side. I have it on every rifle, and prefer it over the Radian one quite a bit.