Recently I found that I had inadvertently thrown away one of these ReefMat 500 chucks when I was changing the roll. To order a replacement was weeks of lead time. I couldn't afford to have my filtration off that long so I created my own replacement.

Since this piece may have some force imposed upon it I printed in PLA+, 5 walls, and 80% infill to ensure it's solid. Also as there's a recess inside the chuck, make sure supports turned on.