Available in 10X (the original and excellent magnification) or 20X (double the original), these are both incredibly wide field eyepieces. The wider field makes them feel more immersive, and it's my impression that the optics are also sharper than the base 10X/20 ones. The 10X/23 upgrade also has a nice integrated diopter adjustment, though it's not really necessary- the scope has this feature built in.