Choose a basket that fits your mug
Look at the basket's depth, width and support points together. A filter should fit the mug and leave your usual leaf portion room to open.
Measure the mug before the basket
The diameter printed beside an infuser may describe its widest support rather than the part that enters the cup. Check the actual opening of your mug, its taper and the depth to your usual waterline. A broad rim with a narrow lower body can prevent a straight-sided basket from sitting properly. A filter that balances at an angle is inconvenient before the water is hot and more troublesome afterwards.
Useful brewing space lies below the waterline. If you usually fill the mug halfway, a shallow infuser may leave some leaves above the liquid. Conversely, a very deep basket can rest on the bottom and make its handles difficult to reach. Look for enough immersion and a secure support at the rim, rather than assuming the largest basket is always the best fit.
Match the mesh to the tea
Fine mesh retains smaller particles, while more open perforations may suit broader whole leaves and allow easy drainage. No filter catches every trace of dust without affecting flow. Consider the tea you use most often, especially if it contains finely cut material. A basket that drains painfully slowly can extend the infusion while you hold it above the cup and wait for the last liquid to escape.
Examine seams, handles and any lid before choosing. You should be able to lift the basket without placing fingers close to the hot drink. If the lid is advertised as a resting dish, check its stability and capacity for drips. Removable parts should come apart as intended for cleaning without requiring force. A simple shape with accessible corners may be more useful every morning than an elaborate novelty form.
Try the ordinary routine
Before the first hot brew, fit the basket into the mug with cool water at your usual fill level. Check that it stays steady and lifts out smoothly. Then use a normal measured portion of tea and inspect the wet leaves afterwards. They should have room rather than forming a compressed plug. Clean according to the material's instructions and replace a filter with damaged mesh or sharp loose wires. A well-chosen basket becomes almost unnoticeable in use, which is often a better sign than a long list of accessories.
