Overview of MSX Floppy Disk drives. Both 5.25" and 3.5" disk drives have been used on MSX, with 3.5" being by far the most common.

Also see: Floppy Disk Drive Interfaces

Supported capacities (with the right drive);

• 5.25" 180KB (Single Sided, Double Density)
• 5.25" 360KB (Double Sided, Double Density)
• 3.5" 360KB (Single Sided, Double Density), also known as 1DD
• 3.5" 720KB (Double Sided, Double Density), also known as 2DD

HD (High Density) capacities are not supported by MSX except by the Daisen Sangyo MX-2021 with its interface MX30B (ultra rare). HD diskettes can be used, but it is advisable to tape (with a non-translucent tape) over the HD hole to prevent problems when used in HD capable disk drives.

For more generic information about Floppy Disk Drives (FDD), you may check Wikipedia.