My OEM battery went bad last year. I went to Walmart and tried to pick the right one with the battery selector they have but couldn't find my VN1700. I bought one similar to that one (the number ended up in 20) because of the size but when I tried to put it, it was too big. I returned it and went to a number of automotive parts shops (Autozone, advanced autoparts and so on), no one had it. I ended up in Napa, they found the right one in the computer. They had the original one for like 150 bucks. Then they offered an after market one, a AGM for around 100 bucks. To my surprise it was shorter than the stock, they provide an adapter to make it taller, and was available everywhere I went, I just didn't know it was the right one. The number was something like EXT-14. The only issue I had is, the motorcycle connector has an U shape, it was not possible to connect with this battery because the battery connector is wider than the U. So I flattened it up with a hammer, I was so tired so I preferred doing this instead of going back to the hunt. No issues so far. So, those are the 3 things you have to take into consideration: capacity, size (so it enters into the box) and connector shape. Hope this helps.