This 7 in. Nylon Garage Door Roller (sold individually) is not the most commonly requested roller. However, when installed it is used to quiet and prolong the life expectancy of your garage door. With a caged 6200Z 10-ball bearing that is rated at 100,000 door open/close cycles, this roller is 10x stronger than the average of 10,000 door cycles for other rollers. The ball-bearing nylon wheel is 75% quieter than steel and non-bearing rollers. The 6200Z bearing protects the inner ball bearing from dirt and grime over time, resulting in the smoother opening / closing of your garage door.