These are on every single ar 15 pattern rifle i own. - Radian Weapons Talon Ambidextrous 45/90 Safety Selector Combo 2-Lever KIT

These are exceptional. The 45 degree is perfect for quickly engaging the safety with my knuckle and it doesn't get in the way like a full sized 90 degree ambi safety does. I actually removed mine just for this reason. They're kind of expensive in my opinion, but they do add functionality and ease of use. Worth the price for optimal performance in my opinion. I have many AR's and they ALL now are equipped with this upgrade.