USPS First Class Shipping (International)?

So I wanna ship something using first class mail but I’ve never done so but anyways is this fine for a shipping box? Green + brown in color box, measuring 7" long, 6" width and, 2 1/2" high. weight will be 5 ounces. Shipping will be to the UK

I am not sure what the cut off for First Class international. It think if its under a pound you can ship first class mail but after that its becomes priority mail. I would check out the USPS website www.usps.com or check out the link below I found.