Sinclair. Call them and they'll set you up correctly.
Yep, I too like the Sinclair. They are caliber specific and in some cases are action specific. Rugers, Remington, and probably a few others are caliber specific only since the bolt sleeves are the same or close enough to work; Kimbers, with such a small bolt, are action specific as well. But for I think $18.00, you get a well designed bore guide that will absolutely protect your rifle while cleaning and has replaceable o-rings that seal the chamber from leaking solvent back into the action.
I am not familiar with Lucas so I can't compare the two. I just know that I am totally satisfied with the Sinclair models.