The "Master" is OK; just don't ask me to bait your hook - I wouldn't want to be called the "Master-Baiter"... (Saw a boat once, with that name. Who, in their right mind, would want to run around in a boat with that name on it?)
At any rate to my surprise, I checked the bill of material and discovered that the CH25 Front Cover "O" ring is NOT included in the repair kit, #CSRK. The machining has been changed on the front cover, and the "O" ring now seals at a different spot, and is a smaller size. The smaller "O" ring is included in the repair kit. If you are re-using your front cover (CH18), simply spit on the "O" ring that's already there in the front cover, and smear it all around the "O" ring with your finger, then re-install the front cover - it's not usually necessary to replace the "O" ring.