Straight Tubing is the connector piece between a Custom Earmold and a Behind-The-Ear hearing aid. It's the part that carries the sound out of a BTE aid down into a person's ear canal. Straight Tubing is designed to work in conjunction with a special "L"-shaped adapter which is attached to the earmold (called a 119 elbow). Straight Tubing should not be used to replace Curved Tubing, and again can only be used in conjunction with the "L"-shaped adapter originally installed in the mold. "Core and Tubing" is not the same adapter and should not be used as a replacement.
Tubing is a critical element of a person's hearing system. Straight Tubing should be replaced at least twice a year, otherwise it gets very hard and brittle and can develop cracks which can cause feedback.
It is easy to replace the Straight Tubing. Separate the earpiece and tubing from your hearing aid (if the old Straight Tubing is really old and stuck on very tight, heat the tubing with a hair dryer - low heat - for a minute or two to soften it up). Once it's pliable, you should be able to disconnect the tube from both the hearing aid's earhook and the "L"-shaped adapter attached to your earpiece. Be careful that you don't pull the "L"-shaped adapter out of the earmold, but if this happens you can reattach the adapter to your earmold and secure it with a small dab of silicone glue (available at most craft or hobby stores). Then you install the new tubing and cut to the proper length.
If you are not comfortable attempting to retube your Custom Earmold, you can always send it in to Lloyds and we can do this for you for a few dollars. Turnaround time is usually one day in house.