Reviews had me worried, but these worked great on 4100 Philips razor
{I purchased these replacement blades directly from Philips, because I had a discount code.  While not purchased from Amazon, these are the same blades I received from Philips.}<br />I used the SH50 replacement blades for a  4100 series Philips razor.  I use my razor not just for my face, but also to maintain my shiny bald head!  Therefore, the razor and blades get quite a work out.  I wanted to replace the blades some time ago, but the negative reviews concerned me enough that I delayed.  Finally, I had to move forward.<br />I wanted to make sure that I was not going to get blades made by a 3rd party, so I contacted Philips directly to ensure I was getting their blades.  The box I received looks exactly like what you see  here on Amazon.  They also gave me a discount code when I contacted them, which is why I purchased from them.<br />Upon arrival, I over-analyzed the replacement process because of comments I had read here.  At least for the 4100, the replacement was an absolute breeze, and I would have been better off not worrying.  You do need to align each of the blades a little, but if you pay attention when you pop out the previous blades, it's simple.  The next time I do this, it will take me less than 60 seconds.<br />In case I didn't like the new blades, I set the old ones aside.  Then I waited--3 days--so there was a solid amount of growth to give these new blades a right proper test!  As I write this, that test was just completed.  The blades passed with flying colors.  It's like the razor was brand new again.  There was no pulling at all.  The shave was smooth, and so is my head.  I'm very pleased with how these blades work with the 4100 model.
Rating: 5 stars