The Cardsharp, designed by Iain Sinclair, is a nifty, little pocket knife that folds as flat as a card. It's less weighty and bulky in your pocket than other foldable knives, but promises cutting power like a scalpel. When we covered the Cardsharp2 back in 2012, it was a stainless steel blade integrated in a polypropylene body. Now it's received a full metal jacket.

The Cardsharp4 makes use of a 2 mm-thick aluminum casing, which Iain Sinclair says adds robustness and strength. The updated knife also has a two-stage Zytel locking mechanism to prevent accidental opening. The new design adds a little weight compared to past models, but at 24 g (less than an ounce), it won't exactly be cumbersome.

As was true with the Cardsharp2, the 2.5-in (65-mm) stainless steel blade is ready to slice and dice with just three folds. The blade technology was originally designed for the medical industry, and while you might not be doing much out-of-pocket surgery in the future, that background makes it sharp enough for all kinds of tasks, including food preparation and cutting through automobile seat belts in an emergency.

On the negative side, the new build has more than tripled the price over the Cardsharp2. The Cardsharp4 retails for US$90. Older, less expensive models are still available for order.

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