A method of assembling a handheld electromechanical surgical device, comprising: providing a hand-held electromechanical surgical device, including: providing a handle assembly including: a power pack (101) including: a core assembly (106) having a plurality of motors, with each motor having a rotatable drive shaft extending therefrom, wherein each drive shaft is parallel to one another； a processor connected to and configured to control each motor； and a battery electrically connected to the processor and each motor； and an inner housing (110) encasing at least the plurality of motors, the processor, and the battery, the inner housing including at least one control interface actuatable to control a functionality of at least one of the plurality of motors； and providing a sterile outer shell housing (10) configured to selectively encase substantially the entire power pack therein, wherein a rotation from each rotatable drive shaft of each motor is transmitted through the inner housing and the outer shell housing, and wherein the outer shell housing includes at least one control button (30, 32a, 32b) for operative registration with each control interface of the power pack； inserting the handle assembly into a receiving cavity of the sterile outer shell housing while maintaining a sterility of the outer shell housing； and closing the outer shell housing to encase the handle assembly.
