13 Ball Nylon Garage Door Rollers (4 Inch Stem) Sealed Bearing (10 Pack) ULTRA-QUIET OPERATION: the 13-ball Precision bearing reduces rotational friction between roller and shaft EXTRA QUIET ROLLERS: reduces garage noise by up to 75% with a Precision 13-ball bearing and nylon roller wheels are much quieter than original equipment garage rollers ULTRA LUBRICATION: bearing lubrication groove contains Mobilgrease XHP 222 grease for enhancing bearing protection in low and high temperature applications (5F to 300F / -15C to 150C) VERIFIED TEST RATINGS: exceeds 10,000 door open/close cycles at 100 pound load STANDARD SIZE: 4-5/8" long shaft, 7/16" thick shaft, 1-13/16" wheel diameter, 1/2" wheel shoulder, 1/2" wheel thickness