We've got a quarter-acre yard with a stubborn hound, and 50 flags was exactly enough to mark the whole perimeter without running short. They went in easy along the fence line, and the bright orange stands out clearly against the grass so the pup actually noticed them during training.
Leo★★★☆☆
The flags themselves are sturdy and hold up well in the ground, which is what I needed for training. My only gripe is that the pack doesn't include any stakes or connectors, so I had to buy those separately. For the price, it does the job, but don't expect a complete setup.