Below is a general manufacturer product group description. Please note the information below is not item specific. Item specifics are above in product details.

MSD Billet and Pro-Billet are the finest performance and racing distributors available. Every feature is designed to provide the best in performance and endurance to top off your ignition system.
Ready-to-Run, E-Curve and HEI Distributors:These are distributors have a built-in module. No ignition control is required and provide more than adequate spark output for street/strip applications.
Pro-Billet Distributors:Most MSD Distributors must be used with an MSD Blaster Ignition, 6, 7, 8 or 10 Series Ignition Control.
General Information
Billet Housing
Like the multiple spark, CD ignition, MSD was the first to introduce a distributor housing machined from a billet of aluminum. MSD uses state-of-the-art Computerized Numerical Controlled (CNC) mills and lathes to create each housing. This procedure produces a flawless, lightweight distributor housing that is accurate to within 0.001”.
Shaft and Ball Bearing Guide
The complete line of MSD Distributors uses a polished steel shaft that receives a QPQ, or Tuftride coating. This process produces a durable finish that reduces friction and resists corrosion. To accurately guide this shaft, MSD uses a sealed ball bearing located at the top of the housing. At the bottom of the housing, an extra long sintered bushing controls the shaft. This combination keeps the shaft spinning smooth and accurately throughout 10,000+ rpm.
Magnetic Pickup
All of the MSD Distributors (except crank trigger models) use a high output magnetic pickup to trigger the ignition system . This pickup is completely maintenance-free requiring no adjustment ever. The pickup is mounted to the base of the distributor housing and plugs directly into your MSD Ignition Control. A trigger signal is created as a precision made reluctor (attached to the shaft) passes by. The reluctor has a “paddle” for each cylinder and when the paddle passes the pickup, a signal is created.
Adjustable Mechanical Advance
One of the most important features of the MSD Distributors is the adjustable mechanical advance assembly. The advance assembly allows you to accurately modify the advance curve to match your specific application. To start with, the advance plate is stamped and machined from chrome moly . Weight pins are then staked in and tig welded in place. This assembly, along with the weights, then receive a corrosion resistant QPQ coating. Nylon weight pads are installed under the weights to ensure smooth movement as the weights are pushed out from centrifugal force to advance the timing. The advance assembly is mounted on top of every MSD Distributor making adjustments a breeze. A variety of advance springs and stop bushings are supplied with each distributor giving you the ability to set up to 24 different curves.
CARB Approved Distributors
MSD offers distributors that have been approved by CARB for use in all the states. Each distributor features a vacuum advance for street economy.