I have some full titanium sliders like the 1st post but they are a normal shape puck..

They are cool, dusk time knee down action is awesome for ya mates to watch. Great until you wear through. I was on a dodgy bit of road once near the coast in kent and it's sort of made of sections rather than tarmac surface. I managed to snag the titanium sheet (where it was worn through and edge was showing) on that particular surface. It gave quite an unsettling kick.