While some riders will opt for knickers in cooler temperatures, others prefer to use a short or bib short with a knee warmer. The advantages are more flexible use options and increased protection on the knee in the cold. This choice should be dictated by rider comfort and the expected weather/ temperature changes during the ride is Louis Garneau's Knee Warmers 2 are compressive, insulated, and water resistant with features such as flatlock seams and silicone grippers that you generally only find in more expensive options.
Garneau uses a polyester material with a brushed inner and less porous outer which offers insulation, wicking, and excellent stretch. This Heatmaxx fabric is then treated with a DWR finish, which delivers water resistance and some wind blocking assistance. The warmer is designed to slip under the hem of the short, while the externally facing silicone gripper holds it in place. You also get reflective elements, low density for easy pocket storage, and UPF 50 protection from the harmful rays of the sun.