Electrodes confusion

[SirLouen]

I'm trying to figure out how the active/passive electrodes sold here could be used in practice.

Since they are not the classic rounded electrodes, at least in the photo they look really strange for me. I've also contacted my friend NFB professional (CEEG, he is using BrainMaster products) and he told me that this looks really strange also, even in his training he did not find this type of electrodes:


How this are supposed to be put in the scalp? Should I solder or ensemble any other piece?
First in the photo, they seem pretty big, maybe they are more little that they seem, but since they are square i feel they wont get a good contact specially in case of hair in the middle.
In the description it says that its a good idea to get an elastic band and sew each electrode to the band, but even though i cant figure out how this square plates could do a good contact with the scalp, since it doesnt seem to have any kind of protuberances or something like this



Also I would like to know, if they are used dry, or if its good to use a electrode gel like?
http://eeg-gel.de/produkte.php#EEGGel

Please give me light about this, I'm really impressed with this system!