This sliding glass door roller assembly is constructed from steel and features a height-adjustable housing. The concaved (grooved) edge wheels installed in these roller assemblies are constructed of plastic and include steel ball bearings for smooth and long-lasting operation. The wheels are designed to glide on a single raised aluminum or steel track. This item includes only one roller assembly per package, but a total of 2 roller assemblies are required for each sliding door. These roller assemblies are used to repair patio sliding doors with missing, damaged or malfunctioning roller assemblies. Installation easy to install with a few simple tools. Refer to dimensional line drawing to match product specifications. This style roller is used on Highlight Doors and similar styled patio doors.