Size Guide:

XX Large
Mount aperture 89cm x 59cm
Frame size 140cm x 90cm

X Large
Mount aperture 69cm x 49cm
Frame size 100cm x 70cm

Large
Mount aperture 49cm x 39cm
Frame size 70cm x 50cm

Medium
Mount aperture 39cm x 29cm
Frame size 50cm x 40cm

Small
Mount aperture 29cm x 20cm
Frame size 40cm x 30cm

measurements will not exceed the above dimensions but are approx.