These inserts are incredible; they truly do shift my weight in such a way that heels are more comfortable, and they provide excellent arch support. This insert works much better than the stick-on gel inserts I bought at the same time (which are also designed to shift weight when wearing heels). i cannot say i have tried them with really high heels; the highest heels i wear are 2-1/4" (and i find even this height very difficult to tolerate). But for me, these inserts are a wonder. I have one pair of shoes i love but have worn only twice in 3 years because they are so uncomfortable, but with the Superfeet inserts i am able to wear them all day comfortably! I also have shoes that provide insufficient arch support and wearing these inserts eliminates the knee pain those shoes usually cause.

I wear a size 9.5 shoe, and this insert in size 8.5-10 fits my foot well. I have worn them with sandals and sling backs, and also with closed-in pumps. With the open shoes, they are not noticeable at all. FYI they stay in place very well. With sandals and sling-backs, i use the velcro dots. With closed-in pumps, they stay in place without velcro. I am able to wear ball-of-foot pads as i normally do (when toe box is too wide) along with these inserts. I am extremely pleased with this purchase and plan to buy more so that i don't have to move them around between multiple pairs of shoes.  One more tip:  the inserts come with two sets of velcro dots for use with two pairs of shoes.  I used the sticky-backed velcro i had among my household supplies to make additional velcro dots for additional pairs of shoes, and this worked very well.