Inline batteries with different + and - connectors
 

It seems that manufacturers are finally listening to those who want a bit more added safety against reverse polarity. The new Yokomo performer packs are made with 5mm + and 4mm - bullets. Does anyone else offer a similar product?
http://www.teamyokomo.com/partslist/rpb/rpb_50s_02.jpg

Long overdue!

I agree....would add another extra layer of security, and cause you to think a little more when it won't fit