This change is found only in the Chinese Benro website, which actually is the most up to date for new releases of products among all Benro related websites all over the word.
It seems that Benro has released a new B series ball head with a Φ 40 mm ball and specifications that put it in line between the existing B1 (with Φ 36 mm ball) and the B2 (with Φ 44mm ball) which I had reviewed in the past.
Therefore, the new model was named B2 and all model numbers starting from the former B2 were shifted up by one digit.
According to the specifications table above, former B2 has turned into B3, former B3 into B4 and so on. There is no indication when the new models will be circulated in the international markets but better make a thorough check before you buy.
As I have seen many times in different fora (forums), a confusion between Benro and Triopo ball head models, please note that although they look similar Benro B1, B2, B3 etc have different specifications than the Triopo B-1, B-2, B-3 etc models.
Given the opportunity, I should mention that all current Benro ball head models, of all series, equipped with an Arca style QR clamp, share the same security lock system on the screw knob.
All models available in the market with a simple screw knob clamp are just old stock.
I hope you found the information useful, thank you for viewing.
Current Benro Ball Heads models as well as older ones are available from DC Photo Stuff on eBay.
Benro B-2 Ball Head Review
Benro B-2 Torque Test.
Benro B-2 & B-Series Ball Head Tips