This new Double Density adapter is a modern update of the old Percom Doubler which has not been available new since 1983.  This new design uses fewer components but its made from all new parts. 

Comes with: LDOS 5.3.1 Double Density System Disk

Or you can choose any of these other Double Density Operating Systems: NewDos/80 V2.0, Dosplus 3.5, MultiDOS 2.10

Video of how to install the Double Density Adapter: https://youtu.be/mcdGd8QOppI

System requirements to use the DDA:

 TRS-80 Model 1 system with 48K Ram IN GOOD WORKING CONDITION

A disk drive.