eBay
Right now, eBay is the best place on the Web to find good used hiking and backpacking gear. Often times, you can find equipment there that has only been used once or twice and the selection and variety is huge and changes daily.

A lot of companies are selling brand new goods on ebay now also. I personally run across some big discounts on sporting goods and other items. The gear is often seasonal closeouts and last year's discontinued items.

It takes only a minute to register with them (which is what you need to do before you buy, sell or email a seller) and registration is free.

See Hiking Listings at eBay

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