The present application is directed to implants with inner and outer members positioned in a telescoping arrangement. The members may include helical supports to selectively adjust the height of the implant. The helical supports offer a large contact surface to prevent inadvertent reduction of the length due to application of a compressive force. In some embodiments, the helical support members may be shaped to facilitate movement of the members to increase the height. The shape may further prevent movement that would decrease the height. Some embodiments may also prevent relative rotation of the members. In use, the inner and outer members are moved apart to adjust the height of the implant to space apart the vertebral members. The members may further be constructed to prevent the members from moving together after insertion between the vertebral members.