Here is a picture of all four drives together. They are all 5¼" drives. There are single and double drives each made by Pace and Opus. You may still come across Pace nowadays as they probably made your digital television receiver if you have one.

The Pace double drive is mains powered so it can be used on a BBC Model B but the Opus one is BBC powered making it suitable only for the Master Series. The two single drives are both BBC powered.

All four drives are housed in BBC-beige coloured casing. In fact, I have never seen a BBC floppy drive in any other colour. The drives themselves are all black except for the Opus single drive which is off-BBC-beige.

Both sets of double drives have the push-down type of drive door. I would not be surprised if the drives inside the casings are identical on both units since they look so similar. I have not yet had any of the drives in pieces. I try to avoid taking them to bits unless I need to have a go at cleaning the heads or changing the drive number links. Whenever I do, there are always some screws left over. I suppose this is the computer equivalent of odd socks.