should I complain

[Greenmantle]

bought a new golf driver
carbon shaft
asked the same pro shop to re-grip from standard to midsize. After getting it home noticed a 4 inch stanley knife cut in the shaft

should i ask them to replace - before I use it?

[fat80b]

Yes. I wouldn’t be happy about that at all. It’ll niggle you forever if you don’t get it sorted

[drmike37]

You'll be sad you didn't when it shatters in your hand and sends splinters into your eyes.

(I think a Stanley knife cut will weaken the carbon fibre. I am not a carbon fibre expert).

[fooman]

Yep see what they say.

[InformationSuperHighway]

100% yes. For sure it was a mistake, but they should be fixing that at their cost.