Trek developed their own BB standard to optimize their frame designs. BB90 has a 90.5mm shell width and 37mm inner diameter and is designed so that the bearings of external cups can hide within the frame.
24mm cranks fit into 37 frames when you have this Mortop Bottom Bracket. The kit consists of two bearings that are pressed into either side of the central opening.

Material: Bearing Steel
Spindle specifictions:

Shimano: Bearings for 24mm spindle
Sram: Bearings for 24/22mm spindle

Shell DIA: 37mm
Shell width: 90mm-95mm
Weight: 

Cartridge Bearing, weight:50g
Ceramic Bearing, weight:47g

BB3724 is not suitable for Tapered Bearings. 

In The Box
2 Mortop  Bearings 
2 Dust alloy covers
2 1mm Ø24mm spacer 
2 5mm Ø24mm spacer
5ml syringe of Nano lubricant
2 Spring spacer (SRAM specification accessories)

Specifically designed for installing 22mm / 24mm spindle diameter cranks (SRAM / Truvativ GXP) the frames without the need for any adapters.