Lees Discard-A-Stones are disposable air diffusers with reusable inserts for attaching to the airline. The Fine Bubble Diffuser creates a flurry of small bubbles; for larger bubbles, use Lees Coarse Bubble Diffusers. Excellent aeration device for all aquariums For use in under gravel filters, corner filters or just as decoration Safe for fresh and saltwater aquariums Includes: 100 stones