How to choose a signal jammer?

I want to buy a signal jammer, which is mainly used to interfere with mobile phone signals and GPS signals. Is there any recommendation?

Topsignaljammer  2022.

There are many types of cell phone blocker, and there are at least a dozen companies specializing in this product. In terms of appearance, there are plastic shell built-in antennas and metal shell external antennas; in terms of power, there are single-channel 2W, 3W, 4W, 5W, 16W and 50W; in terms of performance, there are Only block mobile phone signals, block mobile phone and WIFI signals, block mobile phone + WIFI + walkie-talkie signals, and block mobile phone + WIFI + GPS signals. So where do you use it, how much area to shield, what is the signal strength, and what suits you is the best.