Being deployed to Afghanistan makes it sometimes hard to find the right equipment to work out.  The SPRI ES503R Xertube definetely comes in handy in matters of storage and travel.  I work out everyday, alternating cardio and weights.  I mostly use the Xertube for arms and shoulders; it gives you a wide range of resistance, from hard to I can barely do any bicep curls.  The resistance on it is very high, unless you are really strong, you won't be able to do shoulders presses with it.  The material is very thick and durable.  The handles are made out of plastic, really hard plastic.  I recommed the Xertube if you're looking for a resistance range and don't want to spend the money on different sets of dumbells; or if you're deployed like I am and don't have the appropriate work out equipment.