Prime-Line Products G 3106 Sliding Window Roller Assembly with 7/16-Inch Steel Center Groove Wheel,(Pack of 2)

This steel ball center grooved roller comes secure in a nylon constructed housing. Helps to keep your windows more energy efficient. Fits on Krest Windows.

Nylon housing with 7/16in. diameter center-grooved steel roller | Fits Krest Window | Keeps windows energy efficient | Install 2 per window