I dont know what choice you have and what type of litter you use at present........clumping, wood pellets etc etc.
I use wood pellets but one imparticular that I dont think will be available to you.....Smart Cat and although mant would say the pellets are all the same, they are not and these last longer.
I would tend to stick with what your kittys are used to, pellets, clumping etc...........tbh none last that long