The Sliding Rack Mount have different spacers, including the following:
1. Sliding Rack Mount with 2 x 2'' spacer is suitable for rack between 46 x 46 mm - 66 x 66 mm ( 1.81 x 1.81 inch - 2.59 x 2.59 inch)
2. New Version Sliding Rack Mount 3 x 3'' is suitable for rack between 73 x 73 mm - 79 x 79 mm ( 2.87 x 2.87 inch - 3.11 x 3.11 inch)
Original Version Sliding Rack Mount with 3 x 3'' spacer is suitable for rack between 60 x 60 mm - 80 x 80 mm ( 2.36 x 2.36 inch - 3.18 x 3.18 inch)
3. Sliding Rack Mount with 4 x 4'' spacer is suitable for rack between 81 x 81 mm - 103 x 103 mm ( 3.18 x 3.18 inch - 4.05 x 4.05 inch)
4. Sliding Rack Mount with 2 x 3'' spacer is suitable for rack between 50.8 mm x 76.2 mm ( 2 x 3 inch）
5. Sliding Rack Mount with 3 x 4'' spacer is suitable for rack between 76.2 mm x 101.6 mm ( 3 x 4 inch）
They are all compatible with racks that have side holes ranging from 5/8" to 1".