This pack is designed to give the maximum battery capacity when used in a crane stock. This extra capacity is cheated by larger cells and a 'third leg' that goes in the stock tube. The upside is you'll be able to play for longer without worrying if your battery is going to go flat. The downside is you won't be able to completely retract the stock, as the 'third leg' gets in the way of the last couple of notches.
Taller players who always have the stock fully extended won't find this a problem. Younger players, or those that like to retract the stock fully and sneak through bushes, should choose the 'Zero One 8.4v 1600mAh NiMH High Performance Nunchuck Battery' (ZOBAT8C1) instead. As long as you don't 'spray and pray' throughout your game play this battery will last you all day and means you can retract the stock completely.