12/14/2023: in case some poeple didnt kmow, use a heat gun to heat up and remove previous mirror, thin flexanble metal or plastic shim may be needed to slide under and sepeerarte the mirror from adhesice strip as well, same type of tool that is sold to remove iphone batteries.

13/2023: Added smaller size mirror holder, for 1x2 inch ~1.5mm thick, replacement mirror that grainger sells brand - Ullman it is a little smaller , than the other mirror, i like it better as it is lighter and thinner. cost 1.50$ free pickup .
link to buy:
zoro sells 1.20$ but shipping ....so ..
https://www.zoro.com/ullman-inspection-mirror-replacement-2-l-b-2r/i/G9992446/?utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=free%20google%20shopping%20clicks&campaignid=19976936786&productid=G9992446&v=&gad_source=1&gclid=CjwKCAiApuCrBhAuEiwA8VJ6JrsyP9vviM7Xik4t1h2r7_IrbKLc9czKQXOQZDFkeg_uYmt32sgNjRoCcAAQAvD_BwE&gclsrc=aw.ds

Grainger link
https://www.grainger.com/product/ULLMAN-Replacement-Mirror-Inspection-38VY47?opr=OAPD&analytics=relItems_38VY46&position=1

Black one with MA on the back is older uses little larger mirror
mirror chips easily

dont think threy sell anymore

printed with Sunlu like ABS water washable resin snd nova washable resin, I found mixing them worked the best , came out nice hard than reg resin, 3.5s curious to see if that makes a difference

I am suprised they produced these with plastic mirror holder, but I believe it was to prevent electric current grounding through your body by blind insertion of the mirror into open live conductors

replacement mirror holder for HVAC / tradesmen telescoping inspection mirror, this should be made of steel but if you happen to get a plastic one and it breaks this is a 50cent fix, ,

i drafted replacement used 4k SLA .05mm layers, 50/50 mix of sunlu abs like and regular water wahsable nova grey resin, printed on foto 8.9 ,

I think this will work with FDM .1mm layers from the start of neck to end of sphere, printing upright ball end up, you would likely have to sand / file a bit to get a nice 4.85mm sphere

supprisingly it is holding up better than the original ,
but I plan on printing with resin like ABS water washable Sunlu , when it arrives

fits multiple brands, the ball mount is standard size ~4.85mm , the mirror is standard 1x2 inch ( 25x50mm) rounded rectangle ~3mm thick mirror,

for some reason when i was working HVAC years ago, these were sold by Zoro under a reputable HVAC trade name like yellow jacket or something so I was surprised they were plastic, it broke after first use, zoro has great cust service sent a replacement it broke after first use as well.

Note: what was enginereed wrong: (for engineer fail detectives / and this is where normal people usually should exit the train to avoid a jolt of bordem)

It was likely being manufatured in with metal at specs below, then later produced plastic for HVAC tech use non conductive blind entry tool
using off the shelf 4.85mm ball end to telescoping metal piece, and they created a 5mm ball end on the plastic holder so when clamp is tightened the mirror and telescoping ball , it would hold the mirror portion in a much more firm postion than the telescoping portion as not to lose whatever angle the mirror is adjusted to prior to sliding through a awkward spot.
but this puts to much stress and the plastic and it breaks at the neck, so I designed with a equavalent 4.85mm sphere, ( -.2mm tolerance = 4.65mm actual drafted dimensions) which is working with cheap resin, so enigeering fail - recovered.