ND300 absorptive neutral density filters have an optical density of 3.0, meaning that they transmit an average of 0.1% of visible light. These filters include identical male and female threads on either end so that they can be stacked with other ND filters to achieve various optical densities. Because the glass substrate is absorbing 99.9% of the light that passes into the filter, these filters are not recommended for use with lasers or immediately in front of higher wattage lighting.