These bags are made out of HDPE black poly, 1 7/8" X 1 7/8 x 6.5" with a vent hole 1/2" above the bottom. They were made to my specifications, I wanted to have some that I could use with my greenhouse trays, so, now I can put 16 of these bags in each tray. Bags are gusseted. They will last for many years, the plastic will withstand temperatures as low as 100 F below 0.
When you have a lot of bags to open it is best to use a bag opener. It is hard to make the bottom of the bags square without it. After several prototypes, I came up with this one. It's not hard to make but takes time.
In case you don't want to make that tool, you can buy it. I ship it half assembled, you have to screw in 2 screws on the bottom with a Phillips driver. Unit shipped is not painted.