I've been using KMP gauges for years. I purchase them on eBay. The quality is great, the price is very affordable and the shipping is fast. 
My experience with engine temperature gauges on my D7Es and D6B has proven KMP gauges are more reliable and last longer than the gauges I got from my Caterpillar dealer.
Two OEM replacement temperature gauge failures were the reason for me trying KMP.
I ordered this ammeter yesterday and received it today! 
Craig
 

 
 

Hi Craig.
Are the gauge lenses glass or plastic?
Is the bezel ring chrome or stainless steel? I have had a problem with these rusting in other brands.

I just tested the lens with a very sharp pointed knife. It didn't scratch and it looks like glass. The bezel ring is chrome and looks to be good quality. I've sold my D7E with the older gauges.
The KMP engine temperature gauge on my D6B has been on since Aug. 2022 and still looks good.  The D6B is parked outdoors.
The temp gauge was less than $60 total in '22.
The ammeter was $20. 
Craig

I just took this picture of the D6Bs gauges. The KMP BRAND can't be seen on the temp gauge can't be seen but I put it on 2 years ago. The SW ammeter is no longer working, I will replace it this weekend. I know the oil pressure gauge is rusty, crusty & old but it works!
Craig
 

Finally an update: I've got to say this another case of a "will fit part" that won't fit! I tried to use a KMP ammeter to replace the one on my D6B. It would've worked if the gauge was wired as original with only 2 wires. Mine has 4 wires on one terminal!
 
The working space to replace the ammeter is very cramped.
 
The KMP ammeter has separate terminal nuts and attachment nuts. There is not room to attach multiple wires. Luckily, I found a NOS Caterpillar ammeter. 

The boxes say they are the same but they aren't. 
 
They look very similar but as Old Magnet mentioned the outer ring on the face is chrome and might not last as long.
Craig