The Vel weak phenotype is due to a heterozygous deletion in the same exon, resulting one functional copy of the SMIM1 gene. If a patient who is Vel negative is transfused with Vel positive red blood cells, they may form anti-Vel alloantibodies.
Hearing aids need to be fitted by someone trained specifically in hearing problems. An audiologist or licensed hearing aid provider can make sure your hearing aids fit and work for your type and degree of hearing loss. You also need to consider cost.
They have the answers to that kind of question. And how do you know that is the right hearing aid for you? IF you have a good specialist they will help you decide which one works best for you. It isn't the cost that counts---it is how well you are able to hear with them. AND by the way---you need to wear one in both ears--stereo don't cha know!