Model Number:0703033/0703026 Item Type:Ear Care Item Name:Preformed BTE earmold tube Type:Hearing aids earmold tube Color:Transparent Preformed Tubing BTE Hearing Aid Earmold Tube Tubes Tubing Size: Choose from 3.5 mm OD, 3.3 mm OD and 3.2 mm OD with tube lock All Behind the Ear (BTE) hearing aid tubes harden and should be changed at least every six months. Many people find it beneficial or necessary to change them more frequently. BTE hearing aids become uncomfortable and more difficult to wear as the tubes become progressively stiffer. Also, it is claimed the sound transmission through hearing aid tubes deteriorates as the tubes harden. What Makes Tubes Harden? Oil from the skin and products used on a person's hair cause tubes to harden. Additionally, people who spend more time outdoors find their tubes need changing more frequently because the UV rays from sunlight and extremes in temperatures cause tubes to harden faster. All the tubes in this listing are industry standard size #13 and fit most BTE hearing aids for adults. This Outside Diameter and a name describing the wall thickness are commonly used to identify the different tubes. The descriptive names and Outside Diameters (O.D.) of the tubes referred to in this listing are as follows: Medium Wall - 0.122"or 3.2 mm O.D. Thick Wall- 0.138'' or 3.5 O.D. Notice: Tubes that have been modified, installed, attempted to be installed, have come in contact with a personal hearing aid or earmold or used in any way CANNOT be returned for exchange or refund because we cannot resell Personal Health care Consumables. Package included: 50 Preformed BTE Earmold Hearing Aid Tubes