I like my REI velcro straps. They are thin, lightweight and have a strong grip. But they have to be sized for the item you are strapping. I use them with a mesh bag to hold extra layers on my rack for long day rides, for instance. I can easily pull them tight and the velcro won't slip.

The blue 18 inch strap forms a circle diameter from about 2.5 inches to 4.5 inches, depending how far the black hook section is from the plastic buckle.

The black 24 inch strap's circle ranges from about 6 inches to 4 inches.