red disk is fantastic no go with amber disk.
i have 2 cats both will go on red disk but on amber disk only one will wee the other wont and both wont poo.
I work 12 hour shifts and red disk smells and is full of wee and poo with no accidents. with the amber disk its always clean but they still wont go.... ive gone back to red disk and they both go fine. stayed on red for 6 weeks now and want to progress! I have even tried putting red disk into the toilet bowl to fool them or hide the water but it didnt work.