▁A ▁ 1 : 3 2 ▁car ▁aver ages ▁ 5 ▁to ▁ 6   in ches ▁( 1 3 – 1 5   cm ). ▁ ▁HO ▁scale , ▁a ▁generalized ▁size , ▁originally ▁ 1 : 7 6 - 1 : 8 7 , ▁now ▁usually ▁closer ▁to ▁ 1 : 6 4 ▁scale . ▁C ars ▁vary ▁in ▁size , ▁running ▁from ▁ 1 : 8 7 ▁( gener ally ▁the ▁older ▁cars ) ▁to ▁ 1 : 6 4 ▁in ▁scale ; ▁but ▁they ▁all ▁run ▁on ▁track ▁of ▁approximately ▁the ▁same ▁width , ▁and ▁are ▁gener ically ▁referred ▁to ▁as ▁HO ▁slot ▁cars . ▁A ▁typical ▁car ▁is ▁from ▁ 2 . 5 ▁to ▁ 3 . 5   in ches ▁( 5 . 5 – 8   cm ). ▁Though ▁there ▁is ▁HO ▁racing ▁on ▁commercial ▁and ▁shop - tra cks , ▁probably ▁most ▁HO ▁racing ▁occurs ▁on ▁home ▁rac etra cks . ▁ ▁In ▁addition ▁to ▁the ▁major ▁scales , ▁ 1 : 4 3 ▁in ▁ 2 0 0 6 ▁slot ▁car ▁sets ▁are ▁generally ▁market ed ▁as ▁children ' s ▁to ys . ▁So ▁far , ▁there ▁is ▁little ▁organized ▁competition ▁in ▁ 1 : 4 3 , ▁but ▁the ▁scale ▁is ▁gain ing ▁some ▁accept ance ▁among ▁adult ▁h ob by ists ▁for ▁its ▁afford ability ▁and ▁moder ate ▁space ▁requirements . ▁An ▁average ▁car ▁would ▁be ▁ 4 . 3 " ▁( 1 0 . 9   cm ). ▁ ▁S lot