Earmold impression material is packaged in a variety of forms including equal component systems, tub and accelerator, powder and liquid, individual units, and cartridge material. For those of you thinking about switching to cartridge material or considering a change in cartridge brand, keep the following in mind to ensure you make the correct impression decisions when you are ready to order supplies.
Know the Model of Impression Gun: Two types of impression guns are currently available and include the DM-50 model and the DS-50 or S-50 model. Unfortunately, both gun models look pretty much the same despite the fact that each is designed to 
accept different cartridges. As shown at the right, the DM-50 gun is designed for is designed for cartridges with a square base whereas the DS-50 or S-50 gun is designed for cartridges with a rounded base. Since many manufacturers have cartridge material available for either type of gun, it is important to communicate the type of gun you use when ordering impression material to ensure the correct cartridge is being ordered. To quickly identify gun model, look for the model identification that typically is embossed on one side of the gun on the base (immediately above where the handle and trigger meet). If that information is not available, look at the base of the cartridge material to determine gun model (i.e. DM-50 is square and DS-50 is rounded cartridge base shown above).
Make Sure Mixing Tips Will Fit Cartridge: While cartridge impression material typically includes mixing tips, there may be occasions where it will be necessary to order mixing tips only. There are a variety of mixing tips currently available that not only differ in length, but differ according to the type of cartridge it has been designed to fit. Once again, cartridges designed to fit DM-50 guns require tips with a different attachment configuration than cartridges designed for the DS-50 gun.
What is absolutely frustrating is that the viscosity of the impression material (i.e. how thick or thin it is when freshly mixed) is not specified — Only the hardness after it has cured, in degrees Shore on the A-scale or C-scale.
This is maddening because of the texture of the underlying cartilage, which is depending on both age and years of earmold usage.
I will get back to you about general information regarding what shore value is appropriate for what types of ears; there are some impression materials that are marketed to be more suitable to older ears that have loose cartilage…I will send along those general guidelines. I hope that information will help in your clinical practice