MEGARA is a multi-object spectrograph project for the 10.4m GTC with medium to high resolution: R ~ 5600 - 17000. The instrument operates in three modes that cover different sky areas. The spectrograph is composed by a pseudo-slit, where the fibers are placed simulating a long slit; a slit shutter is placed just behind the pseudo-slit, a collimator, a 162mm pupil where the volume phase holographic gratings are placed, and the camera with the detector. In the actual design, the collimator is composed by a singlet and two doublets and the camera is composed by two doublets and three singlets. The optics manufacturing of the collimator, camera, windows and prisms of the VPH´s will be carried out at INAOE & CIO. INAOE is also responsible of the design, manufacturing and tests of the cryostat. Here we present in detailed INAOE´s contributions to MEGARA, in particular during the current Preliminary Design Phase.