This is waterproof IP5x/IP7x so it don't need any cover for USB/Mic/Speaker port. 'cause U can only put that phone into water around 1metter and 30min. But Sony Z3(only Z3) has Waterproof IP5x/IP8x. It means u can put ur phone into water upto 3metter and without limited of time(means u can let that phone in water countinually without worry). That why they need cover for USB/Mic/Speaker.
Btw, sorry im using phone, so i can't type vietnamess