Rena microfiltration pads for the rena xp external filter seriesr these pads remove all dust particles from the aquarium providing clear and polished waterr you should think about replacing your pad every month to ensure that you are continually keeping these pollutants at bayr suitable for the rena xp series of external filterr rena xp1rena xp2rena xp3rena xp4size 160 x 160 x 15mmr comes in packs of three pads