In a fit of optimism I recently purchased a used Suntour Microlite freewheel -- 7 speed. The seller informed me beforehand that the chain slips on the 15 tooth cog which I subsequently verified. The cog does not look particularly "worn" but the chain does slip under load. I persume the cog cannot be "repaired" so it needs to be replaced to salvage an otherwise very nice freewheel. Does anyone have a source for these cogs, or better yet, can they be replaced with a steel cog? In an alloy freewheel it would make sense to replace the most used cog with a steel one if possible -- as I recall, steel is much better under abrasive load.