Additive Manufacture (AM) comprises a group of technologies that allow to go from a 3D model to manufactured components, creating them layer by layer until the part is complete [1]. Among the advantages of AM, the ones that apply most to astronomical instrumentation are part complexity and consolidation, the addition of functionalities, design freedom and lightweighting capability.

<br clear="all"/> The IAC participated in the H2020 international consortium, within the work package on cooled mirrors for astronomical instrumentation [2], whose completion in 2021 left a series of outputs in terms of preferred technologies and materials, lightweight typologies and a cookbook [3] that includes both design guidelines for additive manufacturing and specific values of the geometrical parameters for the parts to be "printed".

<br clear="all"/> The aim of this paper is to present the whole process since the beginning: from the conceptual design, to the results of the studies carried out on the lightweight mirror samples (with the two typologies and the most promising materials of those studied within the IAC for H2020). Comparisons will be made mainly in terms of metrology, dimensional tolerances and optical surface finishes of the mirrors (roughness, SFE, etc.).