Straight Slots

This slot type has straight sides with equal width through the wall of the casing, it has higher resistance to wear and more economical than keystone, the possibility of clogging is higher than keystone slot.

Keystone Slots

Keystone slot is like a reversed “V” with narrower spacing at the liner surface and wider spacing in the inside casing wall.  Keystone slot is substantially reduce the possibility of clogging and improve work, it is a  little expensive than straight slots, efficiency