Model 454 and 4455 are two different-numbered but functionally and performance-wise identical keyhole devices. Among them, 4455 is an older model. Due to its higher mold cost during development and relatively backward production process, its production cost is much higher than that of 4454, which is also the reason why 4455 is more expensive. As an improved and upgraded version of 4455, 4454 is more flexible and convenient in assembly and use. Assembly instructions for two types of keyhole covers: When assembling the JA series of household sewing machines, they can be used without installing a needle clamp. 

When assembling it on a flat sewing machine, it is recommended to choose a needle holder as well to enhance the convenience of use.