Those work about as well as a 1/4 wave UHF antenna. Not sure I'd agree with the claimed 3dB. Since they don't show dBd or dBi, we'd have to assume the worst.
Essentially, this is what they look like on the inside:
Of course, that is a Laird model, so no telling what cheap Chinese junk Midland is using. But you can't take a 6" long whip and stuff it in a 3" tall can and expect it to work well.
You'd do better with a regular 1/4 wave whip. It'll give you a lot more useable bandwidth, such as covering down to the 70cm band as well as GMRS.