These bags are of excellent quality and are far superior to those found in walmart or other grocery stores. They are 4 millimeters thick and feel heavy duty in hand. The plastic seems used to be very sturdy and the volume is spacious given the size. Mostly, I have used these bags for camping duties and my first aid kit and they have lasted for quite a long time with minimal wear.Also, the zipping mechanism on these bags is MUCH stronger than the ziploc brand and the like. They also seem to zip shut much easier and are easier to aline the zipper. However, when opening these bags, because the lock is stronger, you must be careful not to pull to hard as to not rip the plastice side seam. I have not done this before but it seems like a possibility. Afterall, these are still just plastic bags, they just are more equipped for harsher tasks.One thing I would recommend would be to measure out the sizes of the bags to make sure they are the correct size you intend to purchase. These bags are great for camping, first aid, general orginization and other tasks and will withstand a lot fo punishment before they break. The price is also great for 100 of these bags. Definitely worth the money difference from the 2 mil bags. I highly reccomend this item if you are trying to shelter various small items from the elements.