The string gap is the space between the two halves of the yo-yo body. Some yo-yos have an adjustable gap, allowing the user to increase or decrease the size of this space. A wider gap makes yo-yos less responsive, and lowers drag from the string touching the sides of the yo-yo. Wider gaps are ideal for advanced- to competition-level string trick yo-yos. A narrower gap makes yo-yos more responsive, and can also lower spin time by increasing drag on the sides of the yo-yo. Narrow gaps are idea for beginners' and looping yo-yos. For yo-yos with adjustable string gaps, there are different methods;
- Twist-adjustable: Adjust the string gap by simply twisting the body halves inward or outward. Yo-yos such as the Henrys Viper and the YoYoFactory F.A.S.T. 201 have twist-adjustable string gaps.
- Spacers/Shims: For small-bearing yo-yos in Duncan's Hardcore series, there are spacers in different thicknesses, allowing the user to mix and match them for the desired effect. Similar to bearing spacers, shims can also be used to adjust the string gap, as well as to allow the installation of more advanced bearings, such as the Dif-e-Yo KonKave.