Unique to EnvisionTec 3D dental printers, the PSA (Pre- Stretched Assembly, or Material Basement) is a shallow container that holds only the amount of material that is required for each build. For ultimate results and system performance, the PSA should be replaced every 100 builds. Return the used PSA to 365 Printing using the enclosed return forms and process for a $50 material credit to your online store account. Includes new PSA Vida Release Film.