Walk into most any Crossfit Gym and you'll see some of these.  It seems that no matter what the equipment, it can be incorporated into a WOD.  These parallelettes are especially useful for HSPU [Handstand Pushups], L-Sits, or even as 'stops' for practicing the deadlift with a stick.  And, we've fabricated them to come apart at the base to make them even more portable - now you can throw them in your duffle on the way to the gym, or in your luggage to take on that business trip - no excuses!