The old-style 2-jet carb. appeared on the first 15BB, which was a special rear bearing, front bushing hybrid with the ball bearings running directly on the crankshaft (no inner race). This version was only available for a few years before it was changed to a more conventional dual ball bearing design. A conventional bushing design was also introduced at about the same time. Both BB and bushing models used the old 2-jet carb. The .15's were the last Fox engines to get a carb. update to the MKX series, which occurred in the early 80's. The new carb., referred to in Fox literature as a "Series 15 Mark X", did not have the flat mounting flange and Fox employed an adapter to mount it to the BB engine. (By this time only the BB version of the 15 schneurle remained) As well, the old .15 baffle engine was also updated to the MKX carb. in the last few years of its production. The crankcase on the baffle engine was modified so that an adapter was not necessary.

The Fox 15's, both schneurle and baffle, have been among Foxs' most successful RC egines. All produce excellent power and throttle nicely. No modifications of any kind required on these. Just be sure your fuel contains some castor, and fly happily year after year.
Too bad the baffle piston version is no longer available. Compact, and super light, it would be perfect in a model like the Lazy Bee.