The Penultimate +3 DCR is a multi-function cartridge for the Commodore VIC-20 featuring:

• RAM expansion, Menu selectable 0-35K, in 8 banks, giving a total of 280K
• ROM expansion, 271 assorted programs and utilities, ancient and modern including all TFW8b VIC20 titles and many exclusives
• Full size SD card disk drive with integrated file browser, turbo loader and DOS wedge

It is called "DCR" as a nod to the Commodore 128 DCR, where they also took what was a mainboard and a separate disk drive and combined them into a single board.

You can find a nice review of this cartridge over at the Tynemouth Blog.