I shipped my Zizzo by air as baggage in a heavy canvas bag specially fabricated to carry bikes. Because it is relatively soft, and baggage can be tossed around recklessly by Aairport handlers, I purchased the derailleur protector. When the I opened the bag, the protector, which is made of strong steel, was bent, clearly indicating that the bike had been stepped on or dropped. But no damage was done to the derailleur itself, so clearly the protector served its purpose.