Each Kit comes with four red reusable corner clamps, glue, extra pins, and a 12"x16" frame (Two 1.75" bars of 12" length, and two 1.75" bars of 16" length).
After you own a trial kit, you will only need to purchase the bars you need (you already received the corner clamps in your trial kit, so be sure to keep them in a safe place!). If you need extra sets of corner clamps, these can be purchased separately.