Will the Shimano Deore XT BB-MT800-P Fit My Press-Fit Frame?

If your frame has a 41 mm press-fit shell measuring 89.5 mm or 92 mm across, yes. That covers the vast majority of press-fit mountain frames, and it is the same interface most manufacturers call BB92. The BB-MT800-P is the Deore XT tier of Shimano's press-fit range, built for 24 mm Hollowtech II crank spindles, which means it also works with FSA MegaExo, Race Face EXI, and Surly OD cranks that share the 24 mm standard.

What you get for the XT designation is Shimano's higher grade sealed bearing and a cup design meant to survive weather rather than just spin nicely on a workbench. It weighs 68.2 grams and comes with three 2.5 mm spacers so you can set chainline correctly across different shell widths. Press-fit bottom brackets need a proper press for installation and a bearing puller for removal, so if you do not have both, this is a job worth handing to a shop.