A sight includes an adjusting mechanism including a fixing unit, a cover and an switching unit. The cover includes a groove. The switching unit is disposed on the fixing unit and includes a guiding member and a rotatable disc, wherein the guiding member includes a first end and a second end, the rotatable disc includes a surface, the surface has a first portion and a second portion, the first end faces the groove, and the second end faces the surface. The first end is outside the groove when the second end is placed against the second portion. The first end is inside the groove when the second end is placed against the first portion so that rotation of the cover is constrained.