Just bought me another router to use as an additional access point, so really, I could get by with any firmware that fits (including the OEM firmware), since my main router does all the heavy lifting and this new one will just be for WiFi connections. However, in the general case, how do you know what's included in what version? It looks like the ones below would fit on my RT-N12 D1: It also seems strange that the Mini is actually larger than the MiniIPv6, which is somewhat counter intuitive, since you'd think the MiniIPv6 would be the Mini plus IPv6, thus larger, not smaller. BTW, these RT-N12 D1's are only $14 from Amazon right now, with the rebate. Normally I would have gone with a newer Dual-Band router, but at this price, and with my area being fairly empty in the 2.4GHz band, I figured "Why not an RT-N12?" My computers benefit from higher speeds, and they are all connected via CAT-5e ethernet. I use WiFi for the "minor" devices that don't need great speed - cellphones, laser printers, Fire tablets, eBook readers, Echo Dots, etc. So a router with only 2.4GHz with it's greater range but a little slower in theory, and with only 10/100 WAN speed, is fine with me for an access point in my environment. The $14 price is icing on the cake!