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The Apple Pencil is a nifty little gadget that lets you draw and doodle on all manner of Apple tablets. Now that the iPhone Duo is allowing for Apple Pencils to be used with an iPhone model, the gizmo’s popularity is sure to see a spike. However, just because it’s a tool that interfaces on digital screens doesn’t mean it can’t wear out like a normal pencil. When you’re using Apple’s signature stylus, there are a few signs you need to track to stay on top of wear and tear.

There’s quite the line of Apple Pencils on the market, from the Pro to the USB-C (not to mention the older first and second generations of the Pencil). Despite this variety of models, the detachable tip of an Apple Pencil is a commonality across these many styli. In that spirit, there are a number of common signs that signify whether your pencil is nearing the end of its rope.

While using an Apple Pencil won’t burn up any graphite, the tip of the pencil will still wear into a more jagged shape over time, as opposed to a fresh tip’s even roundness. As a pencil wears down, usage will produce more friction, and the tip will be more rough to the touch. Eventually, an Apple Pencil’s tip will wear down enough to expose the metal underneath — at which point you definitely need a replacement.

If you’re not keeping a close eye on your pencil, this will probably manifest first through that increased friction, but your tip will also lose connectivity over time, which you’ll certainly pick up on as it happens. As these issues pile up, you’ll want to switch to a new tip sooner or later — and hopefully before you accidentally scratch up your screen. In general, you’ll want to replace your tips every two years, though avid users may need a replacement in less than a year.

Despite the gaps in features and price points between different Apple Pencils, all of these models have pretty similar levels of hardiness, both with battery and durability. The tips of the Apple Pencil are the major factor in this equation; fortunately, they can be easily replaced.

Apple sells pencil tips in packs of four for $19, which are compatible with all makes of Apple Pencil. It’s pretty simple to buy these every so often to keep your Pencil in shape, but the replaceable nature of Apple Pencil tips leaves third-party options wide open. Brands like PenTips and Delidigi offer alternatives that emphasize aspects like drawing feel and writing feel respectively; the PenTips Lite offers great precision for drawing (of a quality good enough for artists at Disney) while Delidigi’s Fine Point not only lasts long, but grants precision with a ballpoint feel.