yes. 6390RDS-6832-x fits the generation 4-5 with TLR1 & holosun 507. The x is for the color and draw hand. However I am not familiar with the "K" designation on the holosun.
No, this Safariland 6390RDS ALS Mid-Ride Level-I Duty Holster is not compatible with the TLR-7A. Since retention is based off the light itself, you must use the light the holster was designed for.
No, this Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster is not compatible with a TCM-550XLS.
The Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster would not be compatible with your MR920. You will be able to use a holster that fits gen 4 Glock 19's and accommodates threaded barrels and the TLR-1.
The Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster, does come with the thumb protection wing.
This Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster is not compatible with the IWI Masada. We do carry the C&G Holsters OWB Covert Kydex Holster for the IWI Masada, which can be found by using the link below:
https://www.opticsplanet.com/c-g-holsters-owb-covert-kydex-holster-iwi.html
The Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster for the M&P 4.25" barrel might work with the 4" M&P.
The Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holsters require the compatible light to be installed on the gun to secure it properly in the holster.
The Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster will most likely not fit a Canik TP9 SA. The holster at the link below will fit a Canik TP9 SA.
https://www.opticsplanet.com/weber-tactical-original-range-inside-the-waistband-holster.html?_iv_parent-gun-model=canik-tp9sa&_iv_gun-model=canik-tp9sa-1
We currently do not have a Safariland Model 6390RDS ALS Mid-Ride Level-I Duty Holster for the Glock 17 with a SureFire X300. However, the holsters at the link below should fit a Glock 17 with SureFire X300.
https://www.opticsplanet.com/safariland-model-7360rds-7ts-als-sls-mid-ride-duty-holster.html