Efforts towards further improving the 3D spatial resolution and sensitivity of pre-clinical (i.e., for small animals) Positron Emission Tomography (PET) systems have been pursued during the last years. Most of the available pre-clinical PET systems are built of multiple detectors arranged in a cylindrical geometry with unavoidable gaps (in both axial and transaxial axis) between detectors. These gaps decrease detection sensitivity. Moreover, independently of the scintillator technology employed (monolithic or pixelated), the finite size of the detector modules deteriorates the photon impact determination specially, close to the edges.Aiming to reduce inter-module gaps and edge-effects, we introduced recently a gapless/edgeless scanner design, the so-called ScintoTube I. This system consisted of a single LYSO annulus with a cylindrical inner diameter but 10 outer facets to simplify mounting of standard flat SiPM arrays. The overall performance of the system was acceptable but, the junctions of the facets disrupted the light distribution pattern. To improve performance, we have designed a second prototype, named ScintoTube II, in which both outer and inner facets are cylindrical. The present proceeding summarizes the mechanical design and preliminary evaluation of the ScintoTube II.