Helvetica MH1.B3110.LG 16mm watch strap.
It is possible to fit this strap yourself, it is a little fiddly but relatively easy. Check out this video.
Having trouble finding your strap? More help is here
Helvetica MH1.B3110.LG watch strap, 16mm tan stitched leather.
Helvetica No1 Bold 34mm diameter.
Please check the width of your strap and the diameter of your watch.