Have not been home,so have not worked with tether reel.
The wall thickness is 5mm,but only 20mm on both sides,I have turned the rest down to 3mm.
I am now done with the tether reel,and is working very good.
Was not that hard to make a tether reel with slip ring.
Tether reel is complete waterproof,you can throw it out of water and still waterproof.
Tether reel cost me 400 dollar to make,this includes (Rotary Shaft Seals,Ball Bearings,slip ring,acetal plastic (POM),Stainless steel 316 tube,Aluminium tube and Various things.
Machining of parts is not included in the sum,i have done it myself sow is free.
Do not know how much it had cost if someone has done all the parts, probably it would not have been cheap.