These are for 1.375in x 24tpi tubes that are available from other brands.
1/2X28 and 5/8X24 have spanner wrench holes and are .100 thick protruding from the shroud or pig tube. The Silco mounts protrudes .60 from the shroud or pig tube and are tightened by a 1 1/4″ wrench or adjustable wrench. Silco are meant to fit brakes with the outside threads 1 1/8 x 12 (The joker, The cyclone, Angel and demon, some silcencerco brakes, and battlecomp) Made of Carbon steel. 1.375×24 for SDTA MBTA Protude .50 and are tightend by a 1″ wrench.