The standard Horizon 10W VHF extension speaker black Mls310B is specially designed to adapt to various internal and external container applications. These speakers can be mounted on a stand or flush mounted. They are the perfect complement to any fixed installation VHF. MLS-310 has a built-in 10W amplifier, volume control and on/off switch. It is ideal for applications that require increased volume and clarity. MLS-300 is a non-amplified speaker. Compared with MLS-310, it requires less installation depth and is designed to replace Standard Horizon 201S speakers.