What are Progressive Suspension's 'Heavy Duty' shocks

For Burly 18" apehangers

Stress-free material will help avoid cracking or breaking when exposed to vibrations

3745" stem dia

Some early models with transmission drive

Jims Breather Valve oversize .030" Big Twin L77-99 BT Panhead What are Progressive Suspension's 'Heavy+. 030" oversized breather is used to save worn or damaged crankcases. Manufactured from aerospace quality steel and CNC machined to the JIMS standard. Note: See 978343 JIMS breather hole reamer tool. Note: JIMS breathers can be used with L79 99 style steel breather valve thrust washers. Fits: > L77 99 B. T. (excl. Twin Cam)