I used a Rucksack Pro-tector for a trip to Nepal this year and it was very useful.
First up it did what it said on the tin and protected my rucksack from damage on the carousel and by baggage handlers picking it by the wrong straps. I was confident it helped to stop any opportunistic pilfering from the many pockets and zips too. Carrying my pack to the airport in the usual way it was really easy to slide the protector over and secure it once in the check-in queue and check in was smooth in both directions.
Secondly, once in Kathmandu it was useful to put in the gear I didn't need for trekking and store it at the hotel until my return. On previous trips I've taken a separate holdall for this purpose and the protector saves some space in the pack. It's common for trekkers to do this so it's a bonus use of the Pro-tector.
It had a third use too: for packing the extra stuff I bought on the trip that would not fit into my rucksack. I bought clothes and slid them into the Pro-tector which fortunately had spare room - worth considering when deciding which size to get.
It's a well-made sturdy piece of kit that will survive trip after trip.
The Pro-tector travel pouch is a good design too; very useful for keeping documents, money and cards together and safe while going through the airport and on a day to day basis on the trip. Handy from a trekking point of view too - to store the wads of rupees one needs and to keep the TIMS card, park permits and passport handy for check points. I like to keep the various receipts and tickets as souvenirs and you get quite a few in Nepal from the numerous temples and other sights.
Good kit all round and ethically made in Nepal (which makes a change).