Have used the Safety Seal brand which is in a similar price range to the ones you are looking at. It's a heavy duty all metal kit and replacement parts are available.

http://www.safetyseal.com/store/autokits.htm

Over the years i have used many of the safety seal plugs with out any problems. And while not recommended i even plugged a sidewall puncture once, it got me home. Then i replaced the tire, wasn't going to push my luck anymore than that.

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