Sprocket adapters must be accurately sized to the rear hub diameter. The problem with Huffy, Schwinn and others bought from the big box or department stores is that they might not all have the same hub. The once popular Schwinn Jagaur is an example. They came with three completely different hubs depending on where they were purchased and when.
You'll need to take a caliper to the store and physically measure the rear hub diameter to be certain you order the right one. Most adapter manufacturers have the hub sizes they offer on their websites.
Also the measurement must be accurate, within the thousands of inch to assure the proper fit with no slippage.
Tom