Not that robust...
Rather than use the toy as it was meant to be used, e.g. by grabbing and kicking at it. One of my cats stands on it and rips it to pieces with her teeth. She loves it. but after about two weeks of this, eventually the material gives way and the stuffing comes out. No idea what it's made of though, bit worried that it could harm her. So... careful eyes kept on her and as soon as any hole is made, a new toy is purchased by her loyal cat slave.