MSMA (monosodium methanearsonate) is an arsenic-based grass killer. It kills grassy weeds such as crabgrass and goosegrass without harming most turfgrasses. It contains organic arsenic that, according to the University of Tennessee Extension, is less harmful than aspirin.
There are several styles of hearing aids available, from the smallest - Invisible in the Canal (IIC) to the largest and strongest - Power Behind the Ear (BTE), and the very popular Receiver in the Canal (RIC) - made to fit most hearing losses while remaining nearly unseen.
1 Some also offer wind noise reduction.  Synchronization. For an individual with two hearing aids, the aids can be programmed to function together so that adjustments made to a hearing aid on one ear (volume control or program changes) will also be made on the other aid, allowing for simpler control.