Some Handcuff models like the Tri-Max have a split ratchet with a gate in the centerline.
That gate blocks standard shims and a split shim is required to bypass it.
Sparrows handcuff shims come with a unique citadel head that offers such extreme grip that the shims can be operated with a single finger.
Even with sweaty hands the citadel head prevents your fingers from slipping off the shim.
Works on Smith & Wesson, Peerless, Safariland and countless others
This is for 4 Handcuff Shims
2 x Standard
2 x Split