If dead-set on using mace. I would recommend the gel-foam type.As this will be less likely to blow-back at the user and does a better job of staying where you spray it. They also make versions that contain very very strong dye which will stain the attacker's face making it easier for police to identify them.
http://www.cheaperthandirt.com/product/2-SABMK3GELHUS
(widely available elsewhere, link as example)