A decent low cost linear steel spring from ZCI. These come in a plain plastic bag.
Spring ends are not flattened.
M150 = 490 FPS with 0.2g
When a new batch of springs arrive I generally test one of each power, however occasionally springs may get put into the wrong packaging at the factory.
In cases where FPS is wildly different to that advertised we offer a free returns service so that the spring can be tested and an adequate replacement be sent out.
Wire gauge: 1.68mm