Abstract: The present invention relates to an inline fan housing assembly adaptable for connection with conduits of various diameters. The inline fan housing assembly comprises a connector collar for connection to the inlet or exhaust ports of the fan housings to adapt the fan housings for connection to a variety of conduits having diameters not designed to connect with the inlet or exhaust ports of the fan housing. The inline fan housing assembly also comprises an inner inlet ring for adapting the inlet port of the inline fan housing to direct air into motorized impellor of various sizes mounted within the inline fan housing. The connector collars of the present invention contain one or more steps, each step suitable for connection with a conduit of a different diameter. In one exemplary embodiment, the inner steps of the connection collar are removable thereby allow for increased air flow through the connection.