Buy at Bivethoi: High-quality products help improve your work efficiency and make your work more convenient. Each product of Bivethoi is tested by a dedicated quality inspector before packaging, so you can buy with confidence. Product Advantages: Easy to replace and clean. Give your aquatic pet a safe habitat! Product Specifications: Product Name: Pre-Filter Foam Sponge Rollr Material: Sponge Color: Black Total Size: 8.6 x 5cm / 3.4 x 2 inch (Length*Diameter) Aperture: 2cm / 0.8 inch Package Contains: 4 x Pre-Filter Foam Sponge Rollr Warm Tips: Before you buy, you must check the dimension of water inlet to ensure that it can be used normally These sponges are pre -filtering sponges, so there is only one hole (if necessary, you can cut the closed end with scissors). Please allow us to have 1-3mm error due to manual measurement. Buy with Confidence: It's a great honor for us that you will choose Bivethoi's products. We provide a 30-day free return, and if you have any questions about our products, please feel free to contact us, we will provide you with a satisfactory solution within 24 hours.