Telescopic sights provide some tactical disadvantages. Snipers rely on stealth and concealment to get close to their target. A telescopic sight can hinder this because sunlight may reflect from the lens and a sniper raising his head to use a telescopic sight might reveal his position. The famous Finnish sniper Simo Häyhä preferred to use iron sights rather than telescopic sights to present less of a target. Harsh climate can also cause problems for telescopic sights as they are less rugged than iron sights. Many Finnish snipers in WWII used iron sights heavily because telescopic sights did not cope with very cold Finnish winters.