Digging into the Elites for the Adeptus Custodes
"Chances are, you may already have a Vexilus Praetor in your army! The Custodian Wardens, Allarus Custodians and Custodian Guard kit contain everything you need to build a Vexilus Praetor and a Shield-Captain. Indeed, the Custodian Guard set is almost a Start Collecting! Set for the Adeptus Custodes, containing a Patrol Detachment in a single box weighing in at about 22 power."
the five man Custodian Guard box- the one we have had access to since they have
been available in 40k- has an HQ (Shield-Captain), a single minimum sized
Troops Choice (3-man Custodian Guard) and an Elite (Vexille) in the box,
coming out to 22 power.
via the Warhammer Community