With the use of bi-directional transmission, duplexers allow a transmitter and receiver to share a single antenna. Duplexers also provide good Tx to Rx port isolation. They are useful in applications where there is limited tower space or application costs are at a premium. A duplexer can help by reducing the cost of leasing additional antenna space and by eliminating the cost of an additional antenna. Base station type duplexers offer the best performance but come at the cost of taking up more space and being heavier. Mobile duplexers typically feature compact form factor and at the same time offer acceptable performance.