My 2 (small-medium) cavoodle dogs love this toy - although they chewed the tail and ears (which I then cut off) off the first one, the rest of the toy has remained intact and is one of their favourite toys. So much so, I bought a second recently, so they have one each (the first one has been going almost a year.) Most of their other toys are either ignored or consigned to the bin if damaged!)
The inside is similar (I think - just from the feel, as the toy has remained intact) to a plastic bottle, so is lightweight, crinkable, and is also in 2 parts with a separate squeaker in each side.) Even though mine like to chew it and make it squeak it has never collapsed (like a bottle would) - it seems to be very durable. The fabric has held up very well and there are no tears in the body (though as abov miy dogs do find the ears and tail appealing to chew and eventually I had to cut the half hanging off parts - which hasn't affected the integrity or appeal of the toy.)
I love watching my dogs sit and chew, or squeek the toy; run and toss it, chase each other with it - lots of fun!
It is quite a small toy so probably wouldn't suit a medium-large dog. My 2 are 6-8.5kg cavoodles.
I have seen a similar much larger version of this toy - not sure if it would hold out as well - would suit larger dogs.