Adding shock pads and washers to your drop through is one of the absolute cheapest investments you can make to extending the life of your board. Stress cracks develop over time due to the pressure put on the board by your weight and the trucks. Adding washers to the top and bottom of the nut and bolt disperses that pressure, and the shock pad just adds to the that pressure distribution.
I bought 4 of these packs, and I was surprised you get 2 with every pack, so I ended up with 8. I tried to double stack the pads and create a 1/2" of shock protection, but it doesn't really work. The vibration reduction with 1/2" was not a major noticeable improvement, but did cause issues with wheel bite by raising the wheels higher to the board. You will also most likely need new hardware with these shock pads. With the addition of the 1/4" shock pad and washers I had to get 1.5" bolts.
My ride has gotten smoother and seemingly faster just with these shocks pads. I definitely recommended getting them for your drop through.
Also to answer Drake's questions you only need to buy one set of 2 Shock Pads, you don't need four of them. They will likely work with any Trucks as well.