Soft robots which are made of highly deformable materials are ideal to operate in unstructured environments and to interact safely with humans. This work presents directly 3D printed linear soft vacuum actuators (LSOVA), that are manufactured in a single step without requiring any post-processing and support material, using a low-cost and open-source fused deposition modeling 3D printer. LSOVA have multiple advantages such as high bandwidths (~6.49Hz), high output forces (~27N) and long lifetimes (~21,500 cycles). Finite element models and analytical models are developed to accurately predict the performance of LSOVA in terms of blocked force and linear stroke. The LSOVAs can be directly used in diverse soft robotic applications such as soft artificial muscles, soft prosthetic fingers for prosthetic hands and soft adaptive grippers for gripping applications.