Can an after market master Cylinder be used doe it matter? on 2005 Kia Sportage

My brakes felt off since inhad my master Cylinder replaced. My mechanic said they where fine, but everyone who drives the car says they are bad. I had them checked at another place they said an after market cylinder was used and was wrong and it should have cost 900.00 to fix not 375.00, also that this mistake ruined my brakes. He showed me the part had a plastic piece that was crimped.
What do you think.? Thanks.

As long as the cylinder has the same size piston it shouldn't matter that it's another brand. Get the part number from the one installed and verify it's the correct replacement part for your car. If it's not get the mechanic to install the right one or refund your money entirely. The most likely cause of the issue is air in the system. If what you're experiencing is a soft squishy pedal that goes down further than normal it's probably just air; take it somewhere and have the brakes bled. On some cars the ABS has to be cycled with a special machine to assure there's no air trapped in the controller. The wrong master should not cause damage to any part of the system. If what you feel is something different then describe it.
Thank you so much! I will verify the part and take the car back to my mechanic to have the line bled.