I went to the stabilicers.com website to verify the sizing. XS (kids) is Men 1-3.5, Women 1-4.5, EU 31-35; S is Men 4-7, Women 5-8, EU 35-39; Medium is Men 7.5-10, Women 8.5-12, EU 40-43.5; LG is Men 10.5-13, EU 44-47; XLG is Men 13.5-16, EU 48-50. If you are on the upper number of each size and using a heavy duty boot or winter shoe then I would suggest sizing up.
When I bought mine, I used the size guide from the listing on the L.L. Bean site. Small=women's boot size 5-8; Medium=women's boot size 8 1/2-12. I was a little uncertain because I'm right at the "transition" point between sizes (size 8 boot), but the small was right for me.
Hi~ Speaking as a person who has not had ONE snowflake this entire season -& should have 5' in my yard now, I can give you last years' experience. You say 'STEEP BLACKTOP'. I can't endorse these or any other alleged gripping system because STEEP ICY BLACKTOP is so dangerous. It depends on you, your balancing style, how you move under that shovel and how you transfer your weight.
Last year was ice-o-rama for two months. We all living on a slope. The people who wore stabilicers stayed upright. The one day that I did NOT wear mine, I took a bad fall.
I leave for Maine in 2 weeks. My stabilicers are already packed.
Just the words: steep blacktop,ice & shoveling' make me cringe! Good luck!