Locking midsole and insole assembly

A midsole for a footwear item comprising:

• an upper surface;
• a sidewall;
• and
• an interface between the upper surface and the sidewall, the interface configured to nestingly and closely receive a heel region of an insole of the footwear item, wherein the interface is a fillet region configured to reduce lateral-medial movement of the insole relative to the midsole.

A method of making a footwear item, the method comprising:

• making an insole with a heel region having an insole top surface, an insole bottom surface and an insole sidewall;
• making a midsole;
• and
• arranging the insole onto the midsole, the midsole having a heel region with a midsole upper surface and a midsole sidewall configured to nestingly and closely receive the insole heel region, wherein an interface between the midsole upper surface and the midsole sidewall includes a fillet region configured to support and reduce lateral-medial movement of a heel region of the insole relative to the midsole.