Did I hit my starting gravity? How much alcohol does my beer have? No more guessing, just use these to get tangible data to understand what's happening throughout the fermentation process. Every brewer should have these basic tools in their arsenal.
Thieves are sample-taking devices that can be cleaned & sanitized. Hydrometers and Refractometers will help you figure out the density of your product and help calculate your sugar and alcohol content. And don't forget the test-tube jars to float your hydrometers in!