isotropic pitch-based carbon fibres 

https://doi.org/10.1351/goldbook.I03355
Carbon fibres obtained by carbonization of isotropic pitch fibres after these have been stabilized (i.e. made non-fusible).
Note:
During fabrication of isotropic pitch-based carbon fibre no means (neither mechanical nor chemical) are applied to achieve preferred orientation of the polyaromatic molecules in the fibre direction. They belong to the carbon fibres type LM (low modulus), and because of the relatively low values of strength and Young's modulus this pitch-based carbon fibre type is not used for high-performance reinforcement purposes.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 495 [Terms] [Paper]