A main stage in-line pressure control cartridge. The cartridge selectively controls flow in-line in the same direction as opposed to directing flow at a 90 degree angle like other cartridges. A tubular poppet can be mounted into a body and has a sliding control sleeve that can expose radial holes in the poppet to an open position and to seal the radial holes in a closed position. The cartridge can be configured in numerous ways in order to serve many functions, such as a pressure relief valve, a counterbalance valve, and a flow control valve. The cartridge can also be configured to allow or prevent reverse flow.