The R50 series can take either 12.5mm or 9.5mm drives if it's hot swappable(there is a rubber shield that drops down to fill the extra space). I can't remember if the drive is hot swappable or not on the R50e. If the drive is a hot or cold swappable with a release lever , it will use the enhanced Ultrabay connector and so is not compatible with other manufacturer's products. If it is not hot or cold swappable, then the interface will be the standard laptop optical drive connector and electrically the drive will be compatible. The drive will also be 12.5mm in height. There will usually be slight issues with the front bezel. The IBM drive bezels are cut away to match the mechanical case, while many manufacturers leave the bezel in a square shape.