In the older-style Colorimeter (rounded shape rather than square), the cuvette holder is a plastic insert that can be removed and replaced. The order code for the replacement cuvette holder is CUV-HOLD.
To remove the cuvette holder from your Colorimeter, use a flat head screwdriver to gently lift up and release the two locking tabs that hold the cuvette holder in place. When you install the new cuvette holder, it will lock in place with an audible snap.
Cuvette Holder, order code CUV-HOLD, $3
RELATED TIL ENTRIES
TIL 3403: Do I have an old or current Colorimeter?