The difference in weights illustrates the difference in canvas material. The 5 ounce material is very thin, but it is also the most popular choice for such bags (such as bags for plastic bags). 6 ounces of material are indistinguishable from 5 ounces of material, so if a decision is made between the two, it is usually better for a cheaper 5 ounces of material.
The 10 ounce canvas material is reserved for durable, high quality products that have been used for many years. As time goes by, this material looks better because it is easy to wear. This 12-ounce canvas material is heavy enough to make a more elegant bag that transcends the practicality and simplicity and invades the fashion world.