A type of anti-dilution mechanism. A weighted average ratchet adjusts downward the price per share of the preferred stock of investor A due to the issuance of new preferred shares to new investor B at a price lower than the price investor A originally received. Investor A's preferred stock is repriced to a weighed average of investor A's price and investor B's price. A narrow-based ratchet uses only common stock outstanding in the denominator of the formula for determining the new weighted average price.