A red dot with direct fit goes straight into the optic cut of the slide, without a plate. That keeps the red dot low and leaves fewer screws between the slide and the red dot. Most red dots here use the Shield RMSc or Holosun K-series footprint, which fits slides cut for these red dots, such as the CZ Shadow 2 Carry and P-09 Nocturne. Two red dots are made for one CZ cut: the Holosun SCS P-10 and the Vector Optics Frenzy 1x20x24 for the Shadow 2 OR.
Red dots you can choose
Shield Sights: RMSc, RMSx, RMSw, RMSd, RMSsc, RMS2, SMS, SMS2, SMSc, OMSsc, AMS, AMSc and SIS2, many with glass lenses.
Holosun: 407K X2 and 507K X2, EPS Carry, EPS MRS and SCS Carry, plus the SCS P-10.
Olight: Osight K, S and SE, the SE also with a 6 MOA dot.
Vector Optics: Frenzy-S models and the Frenzy 1x20x24 for the Shadow 2 OR.
Sightmark: Mini Shot M3 Micro in A-Spec and M-Spec Solar.