Itīs not as comfortable as it may seem. They create hot sparks easily but many of them donīt tend to spray them on your tinder in regular use. It may take some training and adjusting to make them do that. So try before you need it. Remember that they are designed to keep the sparks in the gas flow.
I have one of the flints (glued in a small PVC pipe as handle) and a Swiss + Tech Utili Key on my key ring. It works well. The size is suitable for a PSK. A training sample of the flint lasted for about 50 ignitions by now and is still good for more.
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If it isnīt broken, it doesnīt have enough features yet.