Federal Signal's StreamLine Modular Surface Mount Deep Base is designed for flat surface mounting. This base includes two M20 cord grips making this solution idea for mounting these units in a series. To complete your signal, a Federal Signal StreamLine Modular Signal SLM100, SLM200, SLM300, SLM350, SLM400, SLM450, SLM500, SLM600, SLM700 or SLM800 is required.