Our 5000ml Erlenmeyer Flasks are made of Borosilicate Glass (aka Pyrex) which allows for direct boiling and cooling of your starter wort*. These flasks are quality and are graduated at half liter increments. They take a size #10 stopper if you wish to use one but we prefer covering with aluminum foil loosely to allow oxygen to enter while stirring. These are known as student grade labware which means you will find occasional flaws in the glass ranging from bubbles to scratches but none of that should stop you from normal use if you head the advice below. If you want professional lab grade glass, you're going to spend over $100.
*Of course, use of some common sense is appropriate. If you are boiling your starter wort directly in the flask, use a moderate flame. At the end of the boil, turn the flame off and wait about one minute. Cool the flask in a room temp water bath for a minute or two, then cold water, then icewater. This will prevent thermal shock breakage that may occur if you go straight from the flame to icewater.
We will ship these but they are not included in the free shipping offer.