CIRCE is an asymmetric reflective system except for the entrance windows, filters, grisms and the polarimetric components. The entrance window is made of Infrasil 301. This material presents good properties for the polarization system because it is optically homogeneous along three axes (Dn less than 5e-6), and it contains low OH. Its 8 diamond-turned aspheric mirrors offer both excellent throughput and image quality. The collimator consists of two mirrrors with a equivalent focal length of Xm. Two fold mirrors are used in order to fit the envellope in the telescope. The camera with a effective focal lencth of Xm is situated after the filter box situated at the pupil. It consists in 4 mirrors. The filter box contains five wheels: three of them for broad-band (J, H, Ks) and narrow-band filters; one for the Lyot stop and a WeDoWo prism; and one for a Low-Res grism (R=410 @ 1.25um; R=725 @ 2.40 um) and a Mid-Res grism (R=1500 @ J, H and K, for different diffraction orders).