Plug Boot refers to a true race boot. Originally, the race and retail versions looked the same, but the demands of a racer required a stiffer, more powerful boot. To accomodate these demands, the inner mould (the plug) was made smaller so the boot's wall thichness could be increased, hence the term "Plug Boot". Now the term refers to the race boot model which is coloured similar to the retail version, but shares no other features. the are low volume designed to be punched and ground to fit the athlete's feet.