Manufacturer: Jecery. Manufacturer ‏ : ‎ Jecery. #759 in Aquarium Filter Accessories. Exemplary Robustness with Polypropylene: crafted from polypropylene, our filter socks boast exceptional robustness; They’re designed to last, bearing the robust of regular washing and reapplication; Their formulation upholds the integrity of the material while maintaining its functionality over its lifespan.