Water ingress and general wear has necessitated the change of a bottom bracket in one of my roadies. I am generally confused on the whole subject and am trying to educate myself. The bike currently has an SMBB91-41 in it. From what I read, Shimano has muddied the waters with their internal product naming. I was looking online at potentially buying the Premier Ultra Glide bearings which are BB86 twist fit. From what I have read, these are directly compatible. Am I correct here or completely wrong? Thanks for the help.

Disclaimer: I don't do much wrenching and don't plan on doing this work myself.