That explains why they sell anodized parts for this clutch slave, the bore was scratched and the o-ring was shreded. But it was a very simple fix. To remove it you hold the 5mm allen inside the 17mm nut. Remove the nut then take the cover off. A snap ring on the back side and the cylinder will pop out with a little force. Must line up the holes in the cover with the cylinder. Some fine scotch brite and a new O-ring = not leaking.