Hollow core
There is a welded in o2 bung
Stock sound 79 DBA @ idle 90
Along with the ERS padding removal
Seat is made more narrow up front
DRAG SPECIALTIES Derby Torx Bolt Kit - XL MK686 Replacement Insert Hollow coreSocket head bolt sets to meet virtually any custom need Complete motor sets for 07 and later Big Twin include bolts for primary, cam, cam sensor, derby, rocker box, transmission top, transmission side, lifter block and clutch covers Complete motor sets for 87 94 Big Twin include bolts for cam, primary, point, clutch, inspection and chain covers, lifter base, inner primary, top front and rear motor mounts, timing plug and header mount screws Complete