Product review (4 stars): Fits like it should once you find hidden o-ring on plastic of element, and remove old element
Brand name threw me at first.  PROTECH is what I received.  Expected Rheem branding since that is how the product is listed.
When I first looked at the element it didn't appear to include the o-ring seal.  Now what do I do?
Pulled the element out of the packaging which only covers the connector end of the element.  Element itself is not protected/covered.
Looked a little closer and found the o-ring seal was there.  It just blended in to the black plastic.  It was on the opposite side from where you place it for mounting.
So look closely before you worry you didn't receive the o-ring seal.  (And make sure to move it to the correct mounting location too.)
For you first time installers that have never removed an old element, make sure to have access to the 1 1/2" socket and an impact wrench to make the removal a breeze.  Any other option to remove may prove too frustrating and/or painful.