Stahlwille series 20 double ended ring spanners metric drop forged from high grade special steels and chrome plated manufactured to din 838iso 10104 the spanners are optimally hardened in continuous furnaces with no scale build up or skin decarburisation and gently quenched in oil they are extremely strong yet lightweight due to stahlwilles double t profile the unique plating method prevents the problem of chrome flaking the ring end of the spanners are equipped with an anti slip drive profile t