Start with a photograph and a measurement record
Record the guitar model, any known modifications and the installed part’s marking. Take a photo directly above the part and one from the side, with a ruler in the same plane as the dimension you want to show. Use callipers for smaller dimensions and write down the units.
A photo helps identify the design, but perspective and ruler resolution limit precision. If the product drawing omits a critical dimension, ask for it before ordering or modifying the instrument.
Measure the right spacing
E-to-E string spacing is measured centre-to-centre between the outer strings at the saddles. Mounting spacing is measured between the centres of screws or posts. Nut spacing is a separate measurement; it does not need to equal bridge spacing.
Six equally spaced strings have five gaps: 52.5 ÷ 5 = 10.5 mm. Use 25.4 mm per inch for exact conversions and check whether the catalogue’s inch label is nominal. The Telecaster spacing guide gives worked examples.
Use the checklist for the part you are replacing
Compare each relevant measurement with the selected product and option, not just the family name.
Bridges: every mounting-hole position, E-to-E spacing, plate footprint, string-hole position, saddle travel and height range.
Saddles: width, length, height or barrel diameter, screw position, thread and string contact geometry.
Tremolo blocks: height, width, thickness, block mounting holes, arm connection and moving clearance in the cavity.
Ferrules or ferrule blocks: hole diameter, depth, lip dimensions, overall footprint and hole spacing in the body.
Pickup rings and plates: external size, cut-out size, all screw centres, thickness and flat or curved mounting surface.
Fasteners: diameter, thread pitch, usable length and head clearance. Similar-looking metric and imperial threads are not interchangeable.
Check the option and any missing dimensions
The linked ferrule block has separate options labelled 2-1/8, 2-1/16 and 2-7/32 inch. Select the intended option before checking its images and specifications. Its title alone does not identify the option you will receive.
The linked pickup-ring pair specifies a flat bottom, 71 × 39 mm opening, 82 × 38 mm mounting-screw spacing and different neck and bridge thicknesses. Matching only the opening would leave several fitment checks unanswered. Send your measurements, photos and intended product link through the contact page if you need help comparing them.
Frequently asked questions
Is a matching guitar model name enough?
No. Use it as context, then compare the installed hardware and dimensions. Model revisions and earlier modifications can change the parts on an individual guitar.
Can I use a ruler instead of callipers?
A ruler can show the overall layout. Callipers are more useful for small diameters and depths; use a thread gauge or a verified thread specification for screw pitch.
