Please could you let me have measurement of this gasket. Purchased one gasket but wrong one. I have a husqvarna 450 e series.

The dimensions of this gasket are 55mm x 32mm x 1mm. This is a Stihl gasket. The part number you need is 579 75 31 01. https://www.lsengineers.co.uk/gasket-for-husqvarna-135-140-e-440-e-ii-445-ii-450-ii-579-75-31-01.html