1. Would these be good for rack mount high power power supplies applications?

(FCI) In particular the PwrBlade is the industry standard interconnect for blind-mate power supply interfaces.  FCI developed and licensed the PwrBlade connector to make it truly an industry standard.  FCI’s power card edge connector is also an industry standard power supply interface for low profile or 1U applications.

2. What is meant by hard metric?

(FCI) Hard metric can best be described as an ‘equipment practice’ whereby the backplane-to-card dimension is 12.5mm.  The 12.5mm backplane-to-card dimension is an industry standard that is supported by many other connector and products.

(BOB) My understanding of "Hard Metric" connectors are those designed on metric rather than decimal centerlines between the contacts.

Years ago, connectors were commonly based on centerlines such as 0.156, 0.125 and 0.1 inch.  Simply converting these decimal dimensions to millimeters results in "soft metric" equivalents.  The connector did not change, only the way it was dimensioned.

The introduction of connectors such as the Metral connector from FCI changed this to 2 millimeter centerlines.  These connectors were specifically designed in millimeter dimensions and are considered "hard metric" connectors.  Many newer connectors have since entered the market in metric dimensions.