While this product will be usable for the purposes they were purchased for, the size description was not very clear. It would have been helpful to see these "sight glass" balls in comparison to various sizes of sight glasses/tubes. The price of the item was a bit high for what we received but we were accepting of that cost. The cost of shipping was exorbitant. I purchased 6 balls that would fit into a regular business envelope without extra charge, but was charged over $$14.62 and the shipping was not set up as expedited. Attached is a picture as that shows the size of the purchase as compared to a normal ink pen. These items were purchased on behalf of a small volunteer fire department in rural Maine.