For women's sizing...
The 4D 2990s should fit someone who normally wears a woman's size 5.5D boot, and possibly someone who wears a woman's size 5.5B, or 5D, after putting in removeable footbeds.
The 4.5D 2990s should fit someone who normally wears a woman's size 6D boot, and possibly someone who wears a woman's size 6B, or 5.5D, after putting in removeable footbeds.
The 5D 2990s should fit someone who normally wears a woman's size 6.5D boot, and possibly someone who wears a woman's size 6.5B, or 6D, after putting in removeable footbeds.
It's worth mentioning all 2990s posted here are factory 1sts.