Just wanted to let everyone know of the great experience I've had with this antenna. I've used GMRS on and off for years (previously had a license years ago). I've tried MANY antenna as a base antenna, and never found anything that performed well for my particular situation.
I live in a valley, mountains on 3 sides (Alabama mountains, so not huge), and my city and the closest repeater are on the other side of the mountain. My elevation is roughly 700ft, and the closest repeater (21 miles away) is at 755ft. The mountain between peaks at around 1211ft. After many iterations of different antenna, I could never hear the repeater, much less be able to key it.
With the Diamond X50C2, I can hit the repeater from home! Added bonus - it's multi-band, so it will also work on MURS frequencies (I really wanted this since VHF does better than UHF over mountains).
The antenna is pretty wide-banded (advertised as 145-162 and 445-469, but has acceptable SWR outside of this, specifically HAM 2M and 70cm), and right at 5' tall, so it's not a monster antenna. I highly recommend this antenna!