I recently sold my 5066 aquanaut with its original older style non locking clasp. I bought this Patek butterfly locking clasp and straps for it but only wore them a few times. They are over $1500 new. I’m selling for $500. 19mm and fits Patek 5064, 5065, 5066, 5067 and maybe more models. Strap colors are taupe and khaki. Excellent condition and will fit about 7 1/8” wrists. Guaranteed authentic, I have box and receipts for clasp and emails to Stern for the straps