A Wilson Electronics Splitter is a wideband cellular accessory. They allow for two to four indoor antennas to be used in any cellular system with an equal amount of signal across all antenna runs.
These splitters have weatherproof housing, with a solid build allowing for indoor and outdoor use. Waterproof tape is recommended at connection points if used outdoors.
Be sure to pick the right splitter for the number of antennas you intend to add.