Figure 9. Strap length. As the photograph in Fig.6. shows the straps tie around the helmet, as such there is a minimum length they can be. Here the straps for M&Co (bottom 2); an unmarked pair; a P.E.Co Ltd pair; then SLM 1940, 1941 and 1942 are compared. The ruler at bottom is 50 cm; the M&Co straps are ~51 cm (~20”) in length, so with goggles they have a tip to tip circumference of 116 cm (~46”). Easily enough to circumscribe the most voluminous pith helmet. The WWII SLM goggles have the shortest straps, between 42-46 cm.