Civic EG

I'm planning on building a spare ls I have. When I got the motor it came with a set of ctr pistons. My buddy just built a ls using ctr pistons and it runs great.
my question is why exactly is milling the rods or piston required? My friend didn't ask the Guy machining them to do any milling so unless he discovered it himself they weren't milled any.
so is it required or just recommended?
Thanks for any positive input. I really wanna use b16 p30 pistons but idk if my funds will allow at the time.

http://www.ff-squad.com/tech/temp/pistons.htm

yw

That link said nothing about putting those pistons on ls rods. B16 si pistons fit. I'm curious about the type r pistons. Just wanna be positive before I drop them off at the machine shop

Have you measured the rod and the underside of the piston to see if there is a clearance issue?

Taken from another forum :
"B16B or (CTR) pistons will fit B18A rods, but not B18B rods (1994 or higher LS) without getting them modified."