Callaham's fully threaded arms. These arms are designed for use with traditional Fender tremolos and blocks, that use 10-32 threads. This includes vintage Fender Stratocasters plus many others, such as American Standard.
These arms are not what you want for use with Callaham's Enhanced Vintage blocks, which are what we sell on this site. For these blocks, and for products that use these blocks, you want Callaham's Virtual Pop-In arms.