they are still Winchester products, I guess I should have called it a replacement vs aftermarket, but I have done a couple of them and they seem to be holding up much better, maybe because I didn’t crank them down or maybe because they don’t have some form of lock-tight on them, but my loaner SXP and the BILs full time SXP haven’t had an issue since I replaced them.
A warning, they are not fun to get out. Winchester says it’s a factory only repair but we did it ourselves. Heat, a 1” scope ring that you don’t like and a channel lock are needed. We treated it very tenderly as we did not want to bend the receiver.
If you are a DIY guy strip the gun down to the bare minimum without taking the stock off. Use a heat gun on the magazine throat area(we went very slow as we didn’t want to damage the finish) put a 1” scope ring on the magazine tube, about 2” above the action, have 1-2 buddies hold the action/gun and gently turn the magazine tube with the channel lock, using the scope ring for leverage and to protect the tube. If it doesn’t budge, keep gently applying heat and try again. It takes quite a bit of force to get it turning. Once you get it turning a ways, it’s easy. Unscrew the magazine tube fully, the throat will drop out once removed, drop in the new throat and hand tighten, tight but not cranking it down he man style. Reassemble.