If printed with TPU, these rubber inserts are perfect replacement parts for the 1-1/8 and 1 oz. MEC Charge Bars. Also, there is a rubber insert for the Mec Multi-Scale Universal Charge Bar.
Added Fusion 360 file.
In trying to match the softness of the original MEC part, I have found that 10% infill with Wall, Top, and Bottom Thicknesses set to 0.52mm works pretty good. You might have to play a little with your settings to get the right amount of softness/hardness. 100% Infill did not have enough 'give' to prevent binding on the down stroke when reloading.
I have had great success printing these parts with Hatchbox TPU. I suspect they will work fine if printed with any TPU with a Shore 95A Hardness.
I designed this part using Fusion 360. I would offer the other sized Charge Bar rubber inserts, but I only use the 1-1/8 and 1 oz. sizes in my shotshell reloading. Therefore, I didn't have access to the other sizes to model.
These latest versions (I removed the old versions) are better fitted to the height of the charge bar. My first versions, although designed for 1/4-inch height, would always print a little proud of the insert cavity. These print and fit perfectly!