Higher Class UHS-l ; Water-proof, shock-proof, x-ray proof and high/low temperature resistance ;

While the speed rate of a memory card is based on its read/write speed, with security cameras, you really only care about the write speed, which is the rate at which the card writes (records) data to its memory. Too slow speed could cause the video to skip or become sluggish, either of which defeats the reason for having the camera.

Most security cameras are designed for microSD-size cards. For that reason, we will limit the card speed conversation solely to them. The latest microSD cards offer higher storage, allowing longer video recordings (perfect for continuous-use security cameras).
When shooting Full HD or 4K UHD you don't want to worry about slow speeds and dropped frames. Look for cards with minimum write speeds of 70MB/s that support UHS-I Video Speed Class (V30).