Excellent training fins.  Small size makes them easy to carry around, also permits normal kick pattern.  Comfortable.  Appear sturdy - should last forever.  Another great product from Speedo.

The product might be good, but be kids sizes should be offered. I bought it for my son-these fins were too wide for him, so I had to send it back. But size was right-L.

I have size 11-11.5 and ordered the large (grey) ones - perfect fit.
I like the way they are made, appear to be very durable - time will show.
Keep in mind that if you are swimming in a 25yrd pool you will have to do many turns cause you go really fast. But it is an awesome workout on the legs (I assume that 'real fins' would propel you even faster with the same work load - so you get a really good workout with these)

Compareed to other, less expensive speedo fins these do not stand up.  I have little speed with them.

I have a size 12 foot and based on a review by another person also having a size 12 foot, I ordered the gray (Large) size. I could not get them on my feet. Much too tight. I reordered the (Black XL) size and then i could get them on but very tight. I came to the realization that the problem is due to my instep. I have a larger instep than maybe a lot of people and the rubber is not very soft so it tends to be uncomfortable (pinches at my instep area of my feet) This might not be a problem for others, but i do think that the sizes run on the small side. I have ordered a different type of fin. Other than that these probably are nice fins, just not a good fit for me.

Used these today for a kick workout and they were almost perfect.  It did not slow down my kicking tempo by very much but did give extra propulsion from my kicks.  Short enough to do flipturns in and the open heel felt very comfortable.  No blisters/rubbing yet.

Size 11 Men's shoe, ordered a size large.

Only issue is the underside of the fins are both marked as L, but they are both shaped different indicating a misprint.