I-Tungsten, i-molybdenum, i-tantalum ne-niobium yizinto ezibalulekile ezimbonini zezindiza nezokuvikela ngenxa yezakhiwo zazo: ukuzinza kwezinga lokushisa eliphezulu, ukuminyana namandla aqinile, ukusebenza kahle kwazo zonke izinto, nokuvikelwa kwemisebe.