How to choose right aquarium ceramic rings

For sale: Aquarium porous ceramic rings
Price:$25 for 2 kilo
Description:
Ceramic rings are used in filters as a biological media. These rings are highly porous.

Benefits
High porous.
Strong.
Excellent biological filter media.
Non toxic to fish or nitrifying bacteria.
Greater surface area for ahesion of nitrifying bacteria.
Ratio of surface area to cubic measure is greater.
Will not cloud the water.
Increases the capacity of tank.
Dose not disintegrate.

Usage
Media in canister, trickle, tray or box filters
Any filter where biological filter media is required.