So, as the title says, I'm normally not keen on Denis Wick mouthpieces - they're too big, they don't respond brilliantly and they're just all-round much more effort than it's worth to play (not unplayable, but they just make you work hard to get results).
This one is better - it's still a decent amount of work to play, but it doesn't completely drain you the way a 2, 3 or 4 does... the sound is more easily brightened a little bit, but still has that traditional "brass band" darkness that you're expected to have.
Now, it still feels big to me (even though to many players it won't - I play mostly soprano cornet and my most-used mouthpiece is a Reeves 40C which is much smaller diameter than this) but it won't necessarily to a lot of players.
The advertised sizes of many mouthpieces (particularly Bach's) are very difficult to relate to the size that you actually feel on your face when you come to play them, and the Wick line is no different - this doesn't feel equivalent in size to the GR63 series or Warburton 7's that it's claimed "16.00mm" diameter wouldl equate to, it's more like the GR64 and Warburton 5 (if you know how these feel, you'll have a better sense of the size, although the rim feel itself is different again).
Overall, if you must have that classic brassband tone and you'll get strange looks with something other than a Wick in your receiver (it's silly, but someimes it's nice to fit in) then this is the one I would personally go for...
If it fits you, it's the best of the Wicks (IMHO) but as with anything mouthpiece related, it's a very personal choice.