As with all Castelli Products, order one size up from your ordinary size. The italians seem to think the whole world has as small hands as them.

Not sure if this will help but I purchased 2XL (the largest size) and they fit extremely well. Hopefully this will give an idea of the Large/Extra Large and Small/Medium.

Tip of Index to base of palm: ~20cm
Palm width: ~11cm

Note that the material is very stretchy (think wetsuit) so they able to accommodate sizes around their actual printed size. If you want to play it safe and you aren't hulk handed nor have been told to have small hands, just go with a Large/Extra Large.

I used the sizing guide from the Wiggle site and worked perfect… the L/ XL are fine for me, 'normal' sized bloke of 5foot 10

I normally take size large in castelli gloves like their aero ones, but I brought these in size small/medium and they are perfect. Plus with this sort of glove I would recommend slightly snugger fit to keep yours hands warm on those cold days, plus neoprene is a nice stretchy material that will give if need be.

I found them a tight fit despite them being in he range L/XL my hands would normally be M -L

my hand from the wrist to the top of my fingers is 19 cms. and the correct size is m

You can't explain the sizing because they are flawed.Q. How can you have 2 sizes in the one glove when you are unable to adjust them? A. You can't. I bought these gloves and i'm a L, after 20 mins of cycling my hands were in much pain and i had to remove them.