Originally Posted by
Bassbme
Yes, different rods need different sized tips (tip tops) The tube sizes for tip tops are given in 64ths of an inch. Guide sizes are given in millimeters. The size of a guide is determined by the OD of the ceramic ring insert, or the ID of the guide frame where the ring is mounted.
Butt diameters are usually given in 1/1000ths of an inch, but some manufacturers also list them in millimeters. Reel seats are most often given in millimeters, but thousandths of an inch measurements are also given.
I would definitely suggest getting a set of digital calipers. The ones I have, have a mode for fractions of an inch, thousandths of an inch, and millimeters. Being able to switch modes comes in very handy when ordering casting reel seats where you order certain types of seats based on the diameter of the blank (in millimeters). Calipers also come in handy when measuring for winding checks, or if you are turning cork or EVA, or foam cores for carbon fiber grips, where you need to match the diameter of the grip to a reel seat, or trim ring, etc ...