Not sure which size is best? You can always extend your greenhouse later with a Rion Greenhouse extension kit.
The GH40M2 is made for use with the 40 Series Greenhouses (this extension is 4' 4" long).
Note: Single extension kits are not available for the 40 Series. When used with the base, an extension base kit is required (BASE-44M2).
WARRANTY: 7 YEARS AGAINST MANUFACTURER'S DEFECTS.
Helpful Greenhouse Advice