I ordered some 3100s in hope of them fitting my TN30, but they compress the spring in the holder really bad. Almost to the point of crushing it. But, I can use them in my TK75, and so was going to order another set, then thought, I will just order the 3400s since I can’t use them in the TN30.
Then after looking at pics, I can’t tell the difference. All of the numbers I see are the same, and nothing on the batteries I have mentions mah. This is the green protected like these.
linky to batteries
I would not want to get them mixed up, and if I can’t tell the difference, I will just order more 3100s.
Ok, I think I see now, it’s the A or B on the end. I missed that before. 
A=3100
B=3400
In case you weren’t sure. 
LOl. I’m not sure about a lot of things. I spend days researching one item, just to find reviews saying there’s something better, so I’m off again, just to find reviews saying it’s crap. I think it’s like Ford vs Chevy.
After another search, I find the 3400s are a bit longer than what I want, so I’m staying with the 3100s.
I’m think I’m going to stick with Tenergy 2600s for the TN30. Not sure about sag and runtime, but looking at prices on ebay at various brands, I think it’s my best bet. I already have 12 of them, so a few more and I hope my battery searching is over.
Thanks for the reply.
I dont think 3400s are any longer except when they are protected cells. But then again I dont have any 3100s or unprotected 3400s to compare for you.
Yep, my A’s and B’s are the same length (protected)