I have pain at the ball of my left foot under the second (index) toe, especially when doing lot of fumikomis. It slowly got worse with time. Looks like the toe protector is doing its job - after a bit of playing with the positioning of the pressure/anti-slippery points, I think I found the ideal positioning for my problem on the last training. I don't have narrow feet, but the toe protector could be a little tighter for me and I have to readjust it a few times so that the pinky toe stays outside (but as it is a one size for both male and female, I was expecting it not to be too tight). All in all, I am very satisfied coz I can continue training without the pain and swelling.