Since the D5100 has no aftermarket battery grips yet I decided to try a D3100 battery grip and with a simple modification it fit like a glove and fully functions. I did see on ebay where someone was selling a D5100 battery grip for 78 dollars or maybe more but I had not heard it had been released even from 3rd party suppliers so I have to think its a d3100 modified. For $35.00 I got this one and about a minute to modify it. I dont much like the cable for the side shutter button but its not real bad. The feel of it is nice and Im very happy with the results. The battery door from the camera wont fit in the cut out for storage so you will have to store the battery door elswhere and still not a biggie. All in all I like it, it fits the D5100 better than the D5000 battery grips I have seen on a D5000 as you can see no light between the D5100 and the batter grip but on the D5000′s I have seen gaps and the grips was for the D5000. The D3100 and the D5100 use the same battery but the D5000 and D3000 use a different battery. Hope this helps anyone in need of a battery grip but unsure if it will work or not, and sorry for the camera angle… I thought it was int he shot but kept raising it up out of the shot. Thanks