Here at Rehabzone, we have classified our massage balls and foam roller products using the above chart for density/firmness level. This provides a quick guide and reference for users who want a better idea of how the product is like.
Soft: Suitable for beginners or users with lower pain/discomfort tolerance. Users are able to press into the material relatively easily.
Firm: Suitable for users who are familiar with using massage tools. Material can be pressed into, but does not compress too much.
Extra Firm: Suitable for very experienced users for whom softer tools have not much effect. Material is rigid and does not compress much or at all.
Please note that density/firmness is not the only factor to consider. Do see if the product features bumps or spikes which can make the massage more intense, or if it features a vibration function that can have a numbing effect on pain or discomfort.