The Singer 4423 Heavy Duty sewing machine is a mechanical machine with 23 built-in stitches , including a one-step buttonhole function. It features a sturdy metal frame and a powerful motor that can sew through heavyweight fabrics such as denim and leather. The machine also includes an automatic needle threader and a top-loading bobbin system. The Singer 4423 Heavy Duty Sewing Machine Review 2023 is a popular choice for those who need a reliable and powerful machine for heavy-duty sewing, and it is relatively affordable compared to other heavy-duty machines on the market.