Sizing Ground Glass Joints.
    Trying to find out the size of the ground glass joint on your flask or condenser is not as hard as you think. Most all Joints made today follow the same standard. You may have seen sizes as 14/20 24/40. What are those numbers for? It's very simple. The first number is the diameter in mm across the largest part of the ground, frosted, part of the joint. The second number is the length down the frosted area of the joint.

     For example, a 24/40 Ground Glass Joint. If measuring a Outer Joint take a ruler with metric scales and lay it on top of the joint. It should read about 24mm. Now lay it on the side of the joint and it should be about 40mm long. If trying to measure an inner joint you could use calipers or just eyeball it.

    Another thing  to note is that for most joints, if the FIRST number is the same they will fit together. For example a 24/40 will fit a 24/25. a 19/22 will work with a 19/38. It's just that one is longer than the other.  Just be careful when measuring joints around 40mm to 50mm. The sizes are close together, for example 40/50, 45/50, 50/50,55/50.

    One more trick to make it easy. If you have the Outer joint You need a dime and a quarter.
    A dime will sit on TOP a 14/20 and fall INTO a 19/22
    A quarter will sit on TOP a 24/40 and fall INTO a 29/42.
Hope this helps.

dpglassshop