When sourcing a domestic overlocker (serger), prioritize the stitch configuration, typically 2/3/4 thread capability, which allows for versatile seaming and decorative edging. Ensure the machine features a differential feed system (adjustable from 0.7 to 2.0) to prevent puckering on lightweight fabrics or stretching on knits. Look for a high sewing speed of at least 1,200 to 1,500 stitches per minute (SPM) and a built-in rolled hem function that doesn't require changing the needle plate. For high-end models, air-threading technology is a significant selling point as it simplifies the complex looper threading process.