We are now offering Heavy Duty custom extension cords built with one size heavier cable

Black NEMA 10-30 extension cord

Extend your 3-prong Dryer outlet out to your garage. Works well where you need a little more length to plug in your 30A EVSE. At longer lengths voltage drop can be an issue so we are now offering Heavy Duty custom extension cords built with one size heavier cable. Constructed of heavy 40amp 8 gauge cable to minimize voltage drop, with a box type outlet on the end. This is a 30amp cable for 24amp continuous or lower load following the NEC's 80% rule of thumb. Constructed using my super flexible black rubber cord.

https://www.bsaelectronics.com/collections/all/heavy-duty-extension-cords