While I am generally happy with these, there is a small issue with the very top of them. These are injection molded hemispheres and there is a mold ejection knock out ring at the top which leaves a slight indentation into the dome. So, even after sanding these smooth, you will still end up with a slightly distorted flatter area at the top.
All items were received in a timely order and in good condition. They are being used in a summer enrichment program for junior high students called "stem". The 4.5 dia a is being used as a nose protector for an underwater tow vehicle. The size was picked because is fits a pvc pipe coupling. The 3.5 dia is used to house a device called an eyeball. Due wi-fi having limited range underwater this will house a tethered antenna bringing the signal to the surface allowing for students to make subsurface remote observations.
This program will include design, construction, operations and evaluation of the task. There is no failure as it is a learning experience.