It is called Zep crystal heat drain opener, but let me stress you need to be very carefull with this stuff.
you need to wear gloves, and goggles. if your bathroom does not have a window dont use it in there, if it does open the windows and turn on the exaust fan.
to use it you pour the dry crystals down the drain till they reach the top, than you turn on the shower water really low. this will cause the drain to bubble and smoke. so stand clear, once it stops bubbling and smoking you can run it at full strength to wash down any other bits and ensure that the drain is clear. if it isnt repeat untill it is.
also if you have never used this stuff before i would either call a plumber to do it for you or to show you how to do it the first few times. also if you have any pets makesure they are extremely far away from the area you will be doing the drain cleaning. if you have small pets like hamsters which are super sensative to toxic fumes dont do it at all