A housing (15) for connection to a downhole assembly (17), the housing comprising first and second sections (31, 32), the first section (31) being adapted for connection to a portion of the downhole assembly, the second section (32) defining a compartment (23) to receive a downhole tool (11) or component thereof, the second section (32) being configured to provide a path (40) for fluid flow past the compartment (23) as the assembly descends within the borehole, and the first section (31) being configured for fluid communication between a passage in said portion of the downhole assembly and the fluid flow path (40).