I wanted to talk about something I did that I've never seen anyone exactly discuss, using older binaurals (aka metal ear tubes) from a stethoscope in new tubing. I see lots of people replace the tubing, but they tend to keep the third party metal eartips too, which aren't machined the same as OME binuarals.
My 
old tubing had become worn and 
cracked. I let the warranty lapse before sending them for refurbishment (doh!) The consensus of online reviews was the plastic replacement tubes were adequate, but the metal binuarals were lacking. Specifically the tips were not designed the same as Littmann tips and didn't fit littmann rubber eartips (or even the ones included) very well. If your eartips are loose you'll definitely notice a difference in sound quality. Here's a side by side of the littmann binuaral and eartip (left) and third party replacement replacement (right). 
Binuaral, 
eartips.
If you've ever messed with your stethoscope you've realized those binuarals aren't really supposed to come out, and replacement tubes come with them installed. I decided to see if and how I could replace them. I'd recommend anyone doing this use 
nitrate mechanic gloves to get a better grip and protect 
your fingers. Also, don't do what I did and cut the 
binuaral spring. It'll just end up giving you less to grip, and a dangerous sharp edge to avoid.
Edging the plastic along the tubing is a slow process, don't rush it. I wish I had photos or video to share of the process, but I didn't think to do so until after everything was said and done. I might do so if I pick up a used cardiology stethoscope I've been eyeing on the cheap to restore.
The 
end product allowed me to breath new life into a stethoscope out of warranty, for $45 instead of Littmann's $70. About $25 for the tubing and $20 for the replacement diaphragm and earpieces. It also let me pick from a wide variety of colors. The tubing isn't as thick as Littmann's, but definitely strong enough to withstand the removal and insertion of the binuarals.
Source: Original link
