Changing a C-Element (Barco) 

4. Then I removed the four screws on the adapter ring that holds the C-Element and o-ring in place.

The tube with the c-element (and glycol) removed

It's very important that you newer touch the C-Element on the lens just hold it on the outer ring, you should also be very careful with the o-ring that seals the liquid coupling and control that it's not damaged.

The new red c-element with the adapter ring that holds it in place