Mens' slippers?

I went shopping at two supermarkets and coincidently noticed similar grammatical errors.

In one supermarket, the display card reads 'Mens' Slippers' and in the other, 'Mens Pants' were written on a cardboard. Both are wrong grammatically.

To show possession for plural nouns such as men, women, we just add apostrophe s. Hence the above two mistakes can be rectified as 'Men's Slippers' and 'Men's Pants'.