Old Mac CD Caddy

Hello

I recently purchased a old Macintosh Colour Classic with a external CD Caddy (Apple CD 150) and a Macintosh IIvx to create simple MIDI songs as a hobby.
I was wondering if anyone is able to tell me exactly what a CD Caddy is and if a CD tray is needed in order to use it etc.

I have been searching on the net endlessly and have been unable to find anything about them.

Thankies  

1st generation CD drives had a removable plastic holder which you inserted the CD's into.  Then you placed the entire cassette into the drive.  Is that what you have?
Is this the drive?  http://www2.sunrem.com/sun02.w?pt=661-1705&catcode=10100

Here's the caddy:  


http://www2.sunrem.com/sun02.w?pt=678-5059&catcode=10100