I strongly suggest Greenleafaquariums.com, I bought my last 2 drop checkers from them for $20 each, the extra money I spent is well worth it for the following reasons: 1. I'm buying from a trusted US site, a store with well-documented excellent customer service and I got it in 3 days from florida and I live in Cali. 2. It came with enough 4kDH solution to last a couple of years or more. Nuff said...