Giro

I fall exactly in between sizes with a 59cm head circumference. I have a Giro and Bell first generation MiPS helmets in medium that I am replacing. The mediums on me fit fine, maybe a bit high on head but get tight even fully opened if in cold weather with a headband or skull cap. Sucks being in between sizes! Went with a large this time. The Giro large fits well in general, maybe a bit big for me but still have 1-1.5 fingers above brow so should work. Love the quality and build of the top Giro helmets. Price point with my membership status discount on Western Bike Works helps too. Have owned mostly LAS, Giro, and Bell top tier or one step down in models. I will probably order the Giro Aries MiPS in Medium for summer and use the Eclipse large for colder months or some mountain biking. The large on me does give much better forehead, side and back of head protection and Eclipse breaths well too as others have reported. The spherical MiPS is so much better than the original MiPS system. Nice helmet.

I use this helmet for non-draft legal sprint triathlons. I like the ability to easily put a visor on or take it off for travel, different lighting conditions, or for cleaning. it only takes a couple of seconds to put a visor on or take it off. I hold the helmet by the sides where the visor meets the helmet when putting it on in transition to insure I don't accidentally knock the visor off. That has worked and I haven't had any problems in races. I've had other helmets where the visors clip in and are much more difficult to manage.

Synthe MIPS II fit is very good for my rounder head. The straps exit in a good location, adjustability is decent -no issue with slipping when riding over rough patches.

The aesthetic of the helmet profile is traditional and has a wider shape from a front-on view. Those with a narrow facial profile might not like the greater mushroom-top look.

The helmet is not the lightest MIPS available, but it doesn't constantly remind my that my 10yr old non-MIPS LG X-lite one was 45gm lighter.

This is my second Giro helmet, and a step-up from the first. Size is L for a head measurement of 23.25". Fits well, and internal MIPS harness is easily adjustable, with plenty of adjustment up or down. Have used the helmet in transitional fall temps, but not yet on very hot (testing the cooling vents) or very cold (with thicker skull caps) weather rides. There appears to be enough adjustment available for a good fit with both light and winter head coverings. My only complaint: I'd like the option of a minimal, removable visor for sunny days, which my lower-priced helmet had. Without the included visor, I've added a visored cycling cap to my kit. The helmet value came from purchasing this helmet on sale.