The suitable filter for this cat litter box can filter cat litter particles with a maximum diameter of 3mm and a length of 10mm. It supports bentonite and mineral cat litter but does not support tofu cat litter and mixed litter containing tofu cat litter. It is recommended that you choose fast clumping, non- Long strips of cat litter with a granular appearance, such as bentonite type and mineral type cat litter. In addition, when using the litter chamber for the first time, you need to add about 5kg of cat litter. Thank you for your support and trust in Neakasa products.