▁national ▁union ( s ), ▁the ▁number ▁of ▁rep lac ements ▁may ▁be ▁nominated ▁to ▁a ▁maximum ▁of ▁eight , ▁of ▁whom ▁three ▁must ▁be ▁sufficiently ▁trained ▁and ▁experienced ▁to ▁provide ▁cover ▁for ▁the ▁three ▁front ▁row ▁positions . ▁ ▁Prior ▁to ▁ 2 0 1 6 , ▁all ▁substitution s , ▁no ▁matter ▁the ▁cause , ▁counted ▁against ▁the ▁limit ▁during ▁a ▁match . ▁In ▁ 2 0 1 6 , ▁World ▁Rugby ▁changed ▁the ▁law ▁so ▁that ▁substitution s ▁made ▁to ▁replace ▁a ▁player ▁de emed ▁unable ▁to ▁continue ▁due ▁to ▁f oul ▁play ▁by ▁the ▁opposition ▁would ▁no ▁longer ▁count ▁against ▁the ▁match ▁limit . ▁This ▁change ▁was ▁introduced ▁in ▁January ▁of ▁that ▁year ▁in ▁the ▁Southern ▁Hem is phere ▁and ▁June ▁in ▁the ▁Northern ▁Hem is phere . ▁ ▁Equ ip ment ▁ ▁The ▁most ▁basic ▁items ▁of ▁equipment ▁for ▁a ▁game ▁of ▁rugby ▁union ▁are ▁the ▁ball ▁itself , ▁a ▁rugby ▁sh irt ▁( also ▁known ▁as ▁a ▁" jer sey "), ▁rugby ▁short s , ▁so cks , ▁and ▁bo ots . ▁The ▁rugby ▁ball ▁is ▁o val ▁in ▁shape ▁( techn ically ▁a ▁pro late ▁s ph ero id ), ▁and ▁is ▁made ▁up ▁of ▁four ▁pan els . ▁The ▁ball ▁was ▁histor ically ▁made ▁of ▁le ather , ▁but ▁in ▁the ▁modern ▁era ▁most ▁games ▁use ▁a ▁ball ▁made ▁from ▁a ▁synth etic ▁material . ▁World ▁Rugby ▁l ays ▁out ▁specific ▁dimensions ▁for ▁the ▁ball , ▁ ▁in ▁length , ▁ ▁in ▁circum ference ▁of