Features:
OOTDTY  
brand new and high quality
High quality air stone that will create abundant of small to tiny bubbles rather than a limited number of larger bubbles. Can be easily driven by even Nano air pumps, suitable for aquarium, fish tank and circulation system.
Fits for 3/16 in (4 mm) inner diameter tubing.
Increases oxygen and reduces CO2 levels. Durable & washable. Sturdy and non toxic material is safe to your fish.
Please soak the air stone in water for about 15 minutes before usage. Remember that any air stone will need to be replaced every few months as they get clogged with dust, bacterias, and algae.
Multi Sizes: There are 4 sizes to choose for different sizes of fish tanks.

Specifications:
Material: High Temperature Fired Stone
Color: As Pictures Show
Size (Approx.):
20mm-Diameter 0.79in
30mm-Diameter 1.18in
40mm-Diameter 1.57in
50mm-Diameter 1.97in
Weight (Approx.):
20mm-10g
30mm-20g
40mm-60g
50mm-100g

Package Includes:
1 Piece Air Stone (20mm/30mm/40mm/50mm)

Note:
1.Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid.
2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!