Seal and sacrificial components for a drill string

A downhole telemetry tool for transmitting a pressure pulse telemetry signal in a drilling fluid, comprising:

• a pressure pulse generator operable to generate pressure pulses in a drilling fluid;
• the the pressure pulse generator comprises a rotor and stator valve mechanism;
• and
• at least one circumferential recess on the pressure pulse generator, the at least one circumferential recess configured to receive a wear part indicator.

A bottom hole assembly comprising:

• a centralizer collar having a threaded pin;
• a grounding collar having an inner bore for receiving the threaded pin therein;
• a castle nut threadably received by a tapered part of the grounding collar and abutting the threaded pin;
• a landing spider locked in position within the grounding collar by the castle nut;
• and
• a ring spacer placed inside the grounding collar between the castle nut and the threaded pin.