While the No.5® was revolutionary, the #58 is evolutionary. We took our legendary No.5® coupler and shrank the size of the head and knuckle to create a coupler that's even more prototypical. Supersedes product #12.
Converting to scale couplers and KDs are the best.
KD #58s are distinctly the best around.
Springs, and centering brass clips work better and more reliably than any others.