An apparatus and system for accessing a flow system (such as a subsea tree) in a subsea oil and gas production system, and method of use. The apparatus comprises a body defining a conduit therethrough and a first connector for connecting the body to the flow system. A second connector is configured for connecting the body to an intervention apparatus, such as an injection or sampling equipment. In use, the conduit provides an intervention path from the intervention apparatus to the flow system. Aspects of the invention relate to combined injection and sampling units, and have particular application to well scale squeeze operations.