Laundry Detergent Jugs are made of HDPE(High Density Poly Ethylene), the same stuff as fuel jugs. However, it is a heavier material and it is opaque, so it will protect your fuel from ultraviolet rays, and it is less gas permeable, meaning that using a laundry detergent jug will prevent the Nitro in your fuel from off gassing through the walls of the jug.

Also, the pour spout in the laundry jug is a press fit. Once you pull it out, the lid will snug down tighter and make an airtight fit.

I use red, blue, yellow and white detergent jugs for 25% (1/2a fuel), 10%, 5% and FAI fuel respectively. The 50 oz bottles are perfect for sport flying with 40 sized planes because they limit how much fuel you drag out to the field and expose to the dust and changing temperature and humidity.

For the big birds, sometimes it's nice to have the capacity of the 200 oz size detergent bottle.

happy flying.