Linear guideway and dust-proof mechanism thereof

A linear guideway, comprising:

• a rail having two lateral surfaces being opposite to each other;
• a sliding module slidably disposed on the rail along a sliding direction and including:
• a slider including a base portion and two lateral portions that extend from the base portion, wherein inner sides of the two lateral portions of the slider respectively face toward the two lateral surfaces of the rail;
• two circulation seats respectively assembled to the two lateral portions and respectively corresponding in position to the two lateral surfaces, wherein each of the two circulation seats has two rolling channels;
• and
• a plurality of rollers assembled in the two circulation seats and movably arranged in the rolling channels of the two circulation seats;
• two lower dust-proof members respectively corresponding in position to the two circulation seats and respectively abutting against the two lateral surfaces of the rail, wherein each of the two lower dust-proof members is arranged along the sliding direction and has two distal portions respectively protruding from two assembling end surfaces of the slider;
• and
• two end caps respectively fixed to the two assembling end surfaces of the slider, wherein each of the two end caps has two lower slots, and wherein the two lower slots of one of the two end caps respectively correspond in position along the sliding direction to the two lower slots of another one of the two end caps;
• wherein any two of the lower slots respectively belonging to the two end caps and arranged along the sliding direction are respectively sleeved at the two distal portions of one of the two lower dust-proof members and are cooperated with the slider along the sliding direction to jointly have a total length that is within a range from 100.4% to 110% of a length of a corresponding one of the two lower dust-proof members, such that each of the two lower dust-proof members is slidable along the sliding direction relative to the two end caps and the sliding module.