Magnifier 100mm Glass Magnifying Lens
A good hand lens is indispensable to experienced gardeners for pest and disease identification. Most pest managers have a magnifying hand lens on hand at all times. It is one of the most useful tools for a gardener, next to gloves.
A good hand lens allows you to get a close up view of potential pests and diseases as well as beneficial organisms. As you get better at identifying the various critters in your garden you'll come to appreciate your hand lens.