One bag of resin for the 5 liter capacity water softeners.
For recharging instructions, refer to the factory user manual here (ctrl + to zoom), page 10, section 4 and page 11, section 5. What it doesn't mention is the type of salt: coarse kitchen salt (NaCL, sodium chloride).
WARNING: This product can expose you to chemicals including lead, which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.