Natural Path Silver Wings - Colloidal Silver 250 Ppm - 2 fl. oz. (60 mL) Natural Path Silver Wings Colloidal Silver 250 ppm can be used for immune support or health maintenance. Colloidal Silver is 99.9% silver and 0.1% casein. Natural Path/Silver Wings guarantees this to be colloid (0.01-0.001 microns) with the highest percent of the silver particles at 0.002 microns. NP/SW tests for purity particle size and concentration in both house and independent laboratories.