oh bhai you dont need any specific filter.. i'm using an HKS FIlter aur abhi tak replacement ki zaroorat nahi paree.. lekin some of my friend told me kay iska sponge itna mahnga nahi hai.. warna you can get a AC Filter. Cut it in a shap and fit it.. wil work excellent. for further help you can ask Amir Bhai (Tuner)