I am wanting to purchase a Colonial Sporting Clay IMP. MOD. choke tube for a Win. thread system. This type has the 3/8 knurled end on it. I have tried Brownells, Gamaliel, Cabelas, . They do not carry them. They do have Colonia chokes but, not this one. I have tried to contact Colonial direct and they have not answered the phone. Does anyone know of a supplier I can get one from?