Hearing aid/too hissy for me (HA6 Northwood)

Bought these on line.
Works well but there is a constant hissing noise.
This might be my ear canal shape or bad for or faulty aids.
When I do push them in tight though, there is no hiss. So I expect it's a bad fit for my very small ear canals.
Thouroughly cleaned and all accessories.
Collection Times
Anytime, by arrangement.