Aluminum window non tilted 18.5 inch

Many thanks for your post. For your wood lower sashes, you will need our S500-19 Spiral Balances with the Red Tip Option. You will also need the 17-012 balance brackets. These brackets hook on the balance spiral and connect it to the sash. To install these balances, you would drop them from the top on the side of the sash. Use the 33-017 screw to attach the balance tubes at the top. Now raise the sash and have someone hold it up while you attach the bottom bracket 17-012 with a 33-090 screw while the U-shape opening corrals the spiral. With your finger bring up the spiral to the bracket and attach the 75-005 tool. Turn the spiral clockwise three turns and hook it to the fork of the bracket. Repeat the other side and try the sash. If the sash creeps down, raise and hold up the sash and give the balances another turn or two to increase tension. Let us know if you have further questions.