Vertical means that these cakes are designed to shoot straight up. All items are susceptible to wind pressures, which means that shells can alter its course due to wind currents but are still manufactured to be vertical. These cakes are the bulk of the cake selection and perfect if you have tree lines, buildings, or other obstructions within your show-zone. Even with vertical items, it is still best practice to have 30m of clear space all around you.
Unless they are labeled as "rapid fire", vertical cakes tend to fire their contents one at a time. This means that on average, vertical cakes will fire slower, and last longer than fanned or splayed caked.