These external bag vacuum packers require special textured bags, sometimes known as "Embossed" or "Channelled" vacuum bags or rolls. This is because the machine uses the textured surface to draw the air out of the bag.  
We offer a wide range of bag sizes from 150 x 300mm to 400 x 600mm and a range of rolls from 200mm x 6m to 300mm x 6m.  You can cut the bags down to size by using the machines seal only function.
To find out which bag size you require you can request samples of the bags before ordering.  You should try to leave 50mm of clearance at the open end of the bag to allow easy operation.