50hole Low Profile 18-14mm down stem for beakersLow profile down stems with my 48 54hole grid. These come with a clearing hole at the bottom unless stated that it has no hole. This hole is about 5mm big. The function on these are awesome. Its so smooth and has an easy flow when clearing the tube. These come in 1 8 sizes. I have included a pic of how I measure. I measure from the top of the ground glass joint to the bottom. joint size: 18 14mm low profile