DDS packs up to 20GB into one tiny cartridge. This ability is derived from the helical scan technology developed by Sony. Long-term archival storage and a low error rate, Sony DDS tapes employ a magnetic material that has outstanding magnetic transfer characteristics. Key to this performance are Sony's ultra-fine particles and anti-oxidation coating, which is comprised of HDA (High-Density Alloy), HESA (High Energy Stabilized Alloy), and MP+++ (Metal Particle). DDS tapes are made with a non-magnetic layer above the base film to enhance the performance of the magnetic layer. Compared to DDS 3, DDS 4 uses an even thinner non-magnetic layer attaining high output with improved surface smoothness.