Federal Signal's StreamLine Modular Surface Mount Shallow Base is designed for flat surface mounting where cabling occurs from the bottom of the device and where a compact design is required. To complete your signal, a Federal Signal StreamLine Modular top module is required. To complete your signal, a Federal Signal StreamLine Modular Signal SLM100, SLM200, SLM300, SLM350, SLM400, SLM450, SLM500, SLM600, SLM700 or SLM800 is required.