I like cheap tools, but wrenches are one place I ponied up. The Snap-On Flank Drive wrenches don't flex open like cheap wrenches. My header bolts were fiddly to get to, but the wrench wasn't a point of failure on the installation.
https://shop.snapon.com/product/Standard-Handle,-mm/10-mm-6-Point-Metric-Flank-Drive-Standard-Combination-Wrench/OSHM100B
https://shop.snapon.com/product/Standard-Handle,-mm/10-mm-6-Point-Metric-Flank-Drive-Standard-Combination-Wrench/OSHM100B