The main disadvantage of SFP designs comes with the use of range-finding reticles such as mil-dot. Since the proportion between the reticle and the target is dependent on selected magnification, such reticles only work properly at one magnification level, typically the highest power. Some long-range shooters and military snipers use fixed-power scopes to eliminate this potential for error. Some SFP scopes take advantage of this aspect by having the shooter adjust magnification until the target fits a certain way inside the reticle and then extrapolate the range based on the power adjustment. Some Leupold hunting scopes with duplex reticles allow range estimation to a White-tailed deer buck by adjusting magnification until the area between the backbone and the brisket fits between the crosshairs and the top thick post of the reticle. Once that's done, the range be read from the scale printed on the magnification adjustment ring.