Soft materials have been incorporated in the design of robotic systems particularly as a damper, cover or contact pads. With the emergence of soft robotics, which focuses on robotic devices partially or entirely made of soft materials, robotic systems with high deformability, conformability and biomimicry can be realized. By pushing the limits of low cost 3D printing, this study focuses on designing and fabricating low cost, thin-wall, airtight, soft and monolithic fingers and a fully compliant gripper as a one-piece robotic device. Fused filament fabrication method was used to 3D print the soft monolithic fingers and gripper. Their bending and blocking force capabilities were experimentally evaluated. The proposed method can be used not only to 3D print fully compliant inflatable soft robots using a low cost additive fabrication method but also all-in-one piece soft robots ready to operate out of one-step fabrication such as soft grippers and mobile assistive devices with major advantages of low cost, underactuated, and more importantly compliant and highly conformable.