Peter Liontas (pliontas) (Yahoo! FZ10 forum, 6 March 2004)...
The B-300 was originally made for the iS-3000 film camera and discontinued by Olympus about 3-4 years ago. With digital cameras just becoming popular at the time, someone noticed that it worked great with his digicam and hence a legend began. As the ranks of new B-300's dwindled, demand far exceeded supply and the going price of a new B-300 peaked at about $300 in 2002. The list price before it was discontinued was about $125.
The TCON-17 was released in April 2003, and is physically identical to the B-300. Olympus claims that it was re-designed specifically for digital cameras. What that means is unclear to me, although I suspect the optical coating on the lens is different than that on the B-300, perhaps to reduce CA (purple fringing). Much debate centers on whether the TCON-17 is really an improvement or just a re-incarnation of the B-300. Strangely enough, a new B-300 still sells for about $125 on eBay, while the TCON-17 is readily available for $100.
The TCON-14B, specifically made for Olympus' E-10/E-20 digital SLR, is bigger, heavier and less powerful (1.45X) than the B-300/TCON-17 (1.7X) but has much more usable zoom range.
{To actually use any of these tele-converters with an FZ10, you will need a thread-size adapter and/or step-down rings. See sectionsand