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Determine what size objects and how much weight you will carry to school. Also think about what sorts of pockets you will need. College students will have different needs from those of first-graders. Some things to keep in mind include:  Do you need a compartment for your computer? Do you need a place to put your lunch? Do you need places to put pens, keys, or other small objects? Do you want water bottle holders or mobile phone pockets? How many binders, notebooks, and books will you need to carry at once? The fabric a backpack is made of will determine its weight, breathability, and durability.  New synthetic fabrics will last longest, but leather ages with more character. Synthetic fabrics are lighter-weight than leather. If you choose a leather bag it will be much heavier even before you begin to load it.  Synthetic fabrics like polyester and nylon are more water-resistant than natural fibers like cotton.  Natural fibers like hemp are more environmentally sustainable than synthetics. If you care about having an eco-friendly bag choose a natural fiber. Look closely at the closures for the pockets and make sure they are sturdy and easy to close.  Choose double-headed zippers for easiest access. Look for heavy-duty zippers that will hold up over time. Style is an important feature of a school backpack. You will want a bag that looks good and is also similar to backpacks that are currently in style.  Prints are fashionable right now, but consider solid colors too because you will wear the bag every day and it has to match a lot of outfits.  About half of the backpacks sold by one of the biggest companies, Jansport, are black. If you want a sleek, timeless bag that will fit in with the crowd you can't go wrong with a black backpack. Try an eco-friendly bag. Backpacks made from recycled or sustainable materials are very trendy.
Consider size and pockets. Choose a fabric. Check the zippers. Consider current fashions.