Acme # 4011 / 4012 Bottom Roller Assembly for Mirror Sliding Doors. 
Concave 1-7/16 inch Nylon Wheel . Used with Acme Top Guide # 4014. 
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Color: Mill 
Roller Material: Nylon Wheel
Wheel Diameter: 1-7/16-inch
Mount: Bottom
Height: 3-3/8-inch
Roller Edge Type: Concave
Wheel Type: Concave

1989 Patent # 4,850,145

NOTE: The 25143 has a Concave Wheel, The 25157 has a Convex wheel, and the housing is slightly different.