This is a 4 oz bottle of milled fiberglass that is used to strengthen epoxy bonds. New $6.99 (12% off). It is mixed with epoxy glue at a ratio of 1/4 to 1/2 teaspoon per ounce of epoxy. (ratio verified w/product manager KB 4/00). Features: * Increases the strength of any epoxy. * Perfect for adding strength to firewalls, wing hold-down blocks, landing gear blocks. * Easy to use. * Can be smoothed over with isopropyl alcohol for a sleek finish.