SRAM Bleeding Edge
thingiverse
You need a small o-ring. This model worked quite well to me, but it can leak some oil.
Download Model from thingiverse
With this file you will be able to print SRAM Bleeding Edge with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on SRAM Bleeding Edge.