Chapter 4 focuses on the criteria and properties of contact lenses that benefit researchers and industrial perspectives. Firstly, this chapter touches on the industry standards and quality criteria for contact lenses, including the ISO standards used to determine the range of certain contact lens properties such as dimension measurement (lens metrology), lens power, edge profiles and surface imperfections, optical transparency, equilibrium water content, refractive index, oxygen permeability, wettability, and extractable profiles. Next, the essential characteristics of contact lenses will be explained for readers to understand the definition of key properties of contact lenses and some insights into lens metrology, which is the physical characteristics of the contact lens. Moreover, the comparison of contact lens characteristics in the market will be discussed thoroughly, emphasizing the plus points of the contact lens from different manufacturers, which can help contact lens users make a selection when buying suitable contact lenses. Besides, this chapter explores the pioneering research in contact lens properties, exposing the latest research studies that achieve better contact lens properties.