Produced by Advanced Computer Products (ACP) and sold by PRES, the Advanced Plus 3 (AP3) was a Plus 1 cartridge interface using the WD1770 controller, supplied with Acorn's ADFS and a single-sided 3½" disc drive for £99 plus VAT, offering equivalent functionality to the Acorn Plus 3. Announced in late 1987, the product was made possible by an agreement between ACP and Acorn to license the ADFS software. As with many disc interfaces for the Electron, since the interface provided a connector for the drive, this made it possible to connect a 5¼" floppy disc drive (more common amongst BBC Micro owners) or the more typical 3½" drive.