According to New AFSL standard issue in February 2022. A Combination device with a total combined weight of the chemical composition in all tubes greater than 200 grams (7.25 ounces) but not exceeding 500 grams (17.5 ounces) and having an attached single wood or plastic base and any tube greater than 0.50 inches (12.7 mm), must have tubes separated from each other by a distance of at least 0.50 inches (12.7 mm) at the top, bottom and sides. If the inner diameter of all tubes is less than 0.50 inches (12.7 mm) and each tube contains less than 5 grams (0.18 ounces) of composition, no tube separation is required.
Therefore, for the 500g cakes, as long as the powder (single tube) <0.5g, and the inner tube size <0.5″, there will be no tube separation is required. This change can save a lot of space/cost for the zipper cakes.
For more information, you can contact our Red Lantern Fireworks team
Source from: https://www.afsl.org/sites/default/files/AFSL%20Standards%202022-02%2003042022.pdf