Pictures are at the bottom of the page.

The length of the center bolt type of leather straps (see pictures) is measured by the distance between swivel center ( machine bolt) and snap grommet center. These straps requre a hole to go through the accordion casing, to the area inside the bellows.

How to measure the 3 hole plate style strap.

The plate type is surface mounted, and is used to replace the surface mounted metal "chrome" bellows straps, with 2 or 3 wood screws through the plate going into the casing.
The first measurement on the table is the distance between the centers of the swivel and the snap. The second measurement after the "||" symbol is the total length, between the middle of the mounting plate, and the snap grommet center.

You will see that the pictures show 4 male snap grommets come with each pair of straps. The 2 extra ones are to keep the strap out of the way while the accordion is being played. The plate type surface mounted strap has 6 wood screws included for mounting the straps, but not any for the male grommets.

Your accordion probably already has the male snap grommets. In most cases these are surface-mounted, although ,on a few accordions they might have a bolt going all the way through the casing to inside the bellows area. You will need four #4 flat head 3/8-inch length wood screws to mount the male snap grommets. If you don't have any of these screws, or can't get them, I feel sorry for you. Nuts and bolts can be had fom Radio Shack or I will send you some to mount your grommets, if you have missing nuts or bolts, or screws, just ask me for them, and I'll send you some with your order.

And, if you need instructions let me know!
accordiondoc@mindspring.com

Metric vs. English

Measurements of either type strap are pretty accurately expressed in centimeters. The so-called English (inch) measurements were rounded to the nearest one-eighth of an inch.

Center-bolt type of bellows strap.

Plate-mounting type of bellows strap.