I bought 6 1/2, which is my true size for athletic shoes. They are not Sayonaras, but if memory serves, my Sayonaras were a 7. These are a close second. For reference, my true size for sandals/flats/heels is a 6. I go 1/2 bigger for running and cross-training. These are cushioned but sleek. I love them so far (only exercised in them 3 times - all cross-training, but zero concerns!). I have borderline wide feet so not sure about this whole - "these are abnormally narrow" line of commentary. To me - they are sleek, not uncomfortably narrow.As with any shoe - one size does not fit all. So, give them a go! I love them as a replacement to Sayonaras - almost, but not quite, a minimalist running and cross-training shoe.I have only been wearing Mizuno sneakers for walking for five or six years. I own eight pairs and in my experience, I can always order my regular size and they all fit the same. These were noticeably smaller and I had to go up a 1/2 size. Unfortunately, I originally ordered from a discount site that I had to pay for return shipping, which was really annoying. Luckily, through Amazon I was able to order multiple sizes at just about the same price point, but could return the ones that didn't work without the cost. I should have know.These must be a fluke, because I've always been a fan of Mizuno's high quality, but the rubber tread on the shoe began peeling off after a month. I've never seen a Mizuno shoe do that, and I've never seen a shoe do it that quickly. A bit of superglue keeps them together, and they continue to work just fine. I switched to the wave shadow after using the wave rider several times and prefer the smaller heel drop. Similar to other neutral gait shoes like Saucony Kinvara, which is another good one.I used the Wave shadow for 3-10 mile distances, and it's meant for short, speedier work. I usually find after about 6 miles the sole is not thick enough. Otherwise a great shoe for running and cross training. 5 stars if not for the bottom coming off.I wear between a 7.5 and 8, depending on the brand and type of shoe. I ordered a size 7.5 and although these did fit, they were just a little snug. But, I like to wear thicker socks when running. Unfortunately, they didn't have a size 8 at the time so I couldn't exchange them, so I ended up returning them instead with no issues.The brand is known for its comfortable fit and that is true. I’m a size 7.5 and I always buy sneakers in size 8 ( Nike, Adidas, ASICS , these gave me extra wiggle room for my toes)So I bought an 8 to give my feet some breathing room, but it’s just too snug for me. It is just exact. I do not have the extra room I am looking for. Maybe an 8.5 will do but cannot return since I used it already. If you’re a runner this should be your gear.these so far are the best I have had after checking on many other lines, i used to like the ascis tri9 but it got discontinues but so far mizuno shadow waves is my new favorite, i actually ordered 4 pairs and only return one because of the colori give it thumbs i workout at least 4 times a week and run a couple of times a week so for any runner or HIIT workouts, i highly recommend those shoes:)I bought this pair of shoes for a 3 day, 50 mile challenge walk for multiple sclerosis. It rained 2 out of 3 days.This is the first pair of shoes that I was able to wear for the entire walk without switching to a different pair. I only had 2 weeks to break them in and I had only one small blister due to the rain and the wrong type of socks. This is the best my feet have ever felt after this event. This was my 11th year participating in this walk.After reading all of the reviews i went ahead and ordered ½ size bigger than what I normally wear and they fit perfectly! Normally I’m a 6, but I ordered a 6 ½. They are not narrow at all. Fit great!Go a half size up from sayonara.Plus, Super narrow and heel slips out.I’m returning them and continue search for a replacement. This is not it!I order this shoe as it is light, but responsive. I have trusted the Wave Shadow for a number of years for middle distance running and training; distances from 5km to 20kms and always found them the perfect shoe for my style. Highly recommended them if you prefer to run fast and light. 5 stars from me!Great shoe!I have had mizunos all my life! Love them!