The various different connector types, ie 306, 510, 801, 808, 901, eGo are not universal connectors... The 510 and eGo are the two most common types and are probably what you can find the most choices available for. The nice thing about the eGo is it also supports the 510 since that is part of it's design... Of course, you can usually find adapters if needed... but I feel it is smarter to go with the common types so you don't have an issue trying to find supplies.