Made for Gliding / Slider / Sliding Patio Doors with the "tandem design" wheel and roller assemblies - STAINLESS HOUSING AND STAINLESS-STEEL WHEELS and ROLLER ASSEMBLY s Shown Below | Best Corrosion Resistance in Coastal and Salt-Water Environments. Operator Panel Roller Assembly for French Sliding Patio Doors and Other Heavy Patio Doors. Patio Door Hardware and Miscellaneous Obsolete Patio Door Parts for Older Heavy Wood Sliding Patio Doors.  Priced Per PAIR (2 Sets) of Tandem Roller Units.