Detroit, China. Sorry, but those are no good. The cheap quick struts rarely make it more than 10k, and they give quick struts a bad reputation.
Get the name-brand premium quick struts. Monroe, KYB, Gabriel, or Sachs. They last at least 50k.
Monroe's cheaper line Roadmatic may be able to last 30k, so if you absolutely cannot afford the premium parts, at least use Roadmatic instead of the Chinese quick struts.