A sight flow product includes a body having a fluid inlet and a fluid outlet. The fluid inlet and fluid outlet are designed to be connected in-line to fluid pipes within a manufacturing plant or other facility. A cartridge can be located within and conform substantially to a cavity in the body. One or more window assemblies are removably mounted on sides or ends of the body to retain and locate the cartridge within the body cavity. The cartridge can be removed from the body and replaced when either of the window assemblies has been removed. Each of the window assemblies includes a transparent window to allow visual inspection of fluid flow through the sight flow product. A fluid sensing device e.g., a flapper, rotor or condensation drip tube, can be mounted within the cartridge by connection to the cartridge itself or by connection to opposed alignment washers in the window assemblies to facilitate visually inspecting the fluid flow in the sight flow product.