Very good, would now and then villeicht still may be a bit better, but definitely too expensive.

I use auxiliary handles more than 10 years and even today I have that on my Lumix GH3, Nikon D7100, Sony A7R and Oly E-M1.
Earlier auxiliary handles have included 2 batteries. Since the DSLR were also greater. Today, in the smaller housing the grips hold only 1 battery. In the larger DSLRs we have. 2
But actually, in the Olympus auxiliary handle space for 2. If I 2 BLN-1 successively put on the handle, there is room genung not only in length but also in width and height.

But one should not complain: For the other, the handles have a vertical tower which is reingeschoben in the battery compartment so that the battery has to be removed in the camera. It has thus despite auxiliary handle is still only 1 battery and only the handle for portrait format as an advantage.
At Olympus has thought and omitted this tower, the battery in the camera can remain and continue to be used.
You can choose which of the two batteries is used first even in the menu.

Well, there are customers who complain in their review that the handle must be removed in order to change the battery in the camera.
What can I say? That you have to take off the watch in order to change the battery, or stop the car to mount the Winteräder? In fact, it creates the acrobatic motorcycle squadron of police Hamburg to change the side wheel on a side-car driving. Since it does not go with the Olympus be deducted by many stars!

Since I have the comparison with other brands in mind, I can tell that the auxiliary handle of Olympus compared deserves 5 stars.
Apart from these 2-battery-using the part is very high quality and accurately, both in terms of form and color.
It also sits perfectly and bombproof.
It has two function wheels, of course, with triggers, 2 function buttons and a lock, so that is not snapped accidentally.
It's all plastic, so no comparison with the heart milled alloy wheels of the camera. But the pegs are clear and the buttons well sprung. A storage space is also available for the rubber cover of the camera, because the contacts on the bottom of the camera must first be free.

And however, the handle could have been even better. eg. by
- 1 connector for connection to the socket
- 1 storage space for the plastic cap that protects the contact pins of the auxiliary handle in case of non-use
- 1 spare battery included.
That would be the price of approx. 200 Euro in there, because good no-name auxiliary handles usually costs 50-70 euros and it also money is earned.

And since we are at the price where it all ends up, though the Olympus handle costs no more than a big one for a Nikon, but also no less.
I think as the other customers that at the price, Olympus quiet 1 additional battery could spendieren.
And that's why I prefer from 1 star, just like the other customers.

PS: In order not to lose the cover of the pins, I keep it in the package. This is not ideal but better than in your pocket.