In Britain the grades for outdoor climbs generally use a different system and again this is because of the history of the development of the sport in this country. The system goes from 2,3,4a,4b,4c,5a,5b,5c,6a,6b, for technical grades (eg. The difficulty of the moves) but these numbers are different to the indoor numbers with for example 5b outdoors in Britain being about equivalent to 6a at the climbing wall.  Outdoor climbs in Britain also use a subjective system in conjunction with the above said numbers to grade the seriousness of climbs. These go Difficult(D), Very Difficult(VD), Severe(S), Hard Severe(HS), Very Severe(VS), Hard Very Severe(HVS), through to the Extreme grades E1,E2,E3,……. Which again are open ended.