This specification is represented on the card as a number inside of the letter “C.” It represents the minimum write speed and is most important to those shooting video or very large images in succession (burst mode).
There are four classes: 2, 4, 6 and 10. The number represents the minimum sustained megabytes per second (MB/s) write speed — the higher the number, the faster the sustained speed.
Other cards will possibly work, however there is a good chance that you will possibly have distorted video or issues with them as the speed will not be up to par. Especially if trying to record in 4K.
I have a Blade Chroma. The Chroma utilizes the CGO3 camera as does the Q500.
In my Blade Chroma 4K I'm currently using this card:
After doing testing via CrystalDiskMark the card I'm currently using has a 20Mb/s average faster write speed. The write speed is very important if recording in 4K. This card has served me well and is quite cheap at this time on Amazon. Hope this helps.
I also recently purchased a 2nd 128GA/AM card as a backup through E-bay. The price with shipping on this can't be beat by Amazon. Haven't gotten it yet but I will be testing it as soon as it gets here.