In the integumentary system, the components that share a common function are sebum and sweat. Both sebum (an oily substance produced by sebaceous glands) and sweat (produced by sweat glands) play roles in maintaining skin health, regulating temperature, and providing a barrier against environmental factors.
While the other pairs mentioned (scales and follicles, hair and horns, feathers and fur) are components of the integumentary system, they do not share the same specific functions as sebum and sweat.