Air Stones & Check Valve Be the first to review this product.   Conventional air stones aeration available in various shapes and sizes. Thanks to their porous structure, the air stones produce seed-pearl air bubbles. Easy to install thanks to the long tip compatible with the diameter of most aeration tubes. Recommended for all models of aerators. Select* Check Valve Roller M1 25x50mm Roller M2 25x30mm Roller S 15x25mm Sphere 20mm Sphere 30mm Price : R34.00R30.00 Discount : R4.00 (11.76% off) Qty :- 1 2 3 4 5 6 7 8 9 10 11 12 Add to Cart IN STOCK, Usually Leaves Warehouse the Next Business Day. Allow 3-4 Business Days for Delivery.