Quick sell is an option in the silo the sell the materials stored there. You are able to "quick sell" 5 sets of materials each hour. The hour begins counting down when you sell your first item using quick sell. Once the hour expires, the timer will reset and you can sell 5 more items.
The quick sell price is half of the base price of the item. This is a good option if you need to free up space fast and don't want to use your market slots, or if you have items that don't sell on the market.