Proflow tight access header bolts, available in Chromoly or Stainless steel with small diameter washers are the pefect choice when you have large tube headers with very little spanner access to tighen pipes. Once you purchase a set of these it will be hard to go back to using traditional 3/8 headed bolts. You can always start a bolt with a open ended spanner if need be, but once its snug, always pull up tight with a ring spanner