A screw-in, direct acting, ball type in-line check valve. Main use is as a blocking or load-holding device. The CVB0.G18 allows flow passage from port 1 to 2: the cartridge has a fully guided check which is spring-biased closed until sufficient pressure is applied at port 1 to open to 2. The flow is blocked in the opposite direction (2 to 1). Reserved installation is possible (except for size G18) yet not recommended.