How to Cut a WatchGecko 400 Rubber Watch Strap 

A great quick guide Richard, if I could make one small suggestion though and that might be to measure the buckle or clasp to the mid point for the fine adjustment to the hole that the strap will fix to, this would give that little more wiggle room but as you mentioned you added a little bit anyway. You can always cut a little bit more off if needed. Good stuff. I'll have to have a look at these straps as the cut to length save having that extra bulk under the clasp.

Important to say pins must be in when you cut so it does not deform 😉 I was lucky enough to be able to use a professional rubber strap cutting tool which gives a perfectly straight cut in all directions.

My advice would be to practice the cut for the safety clasp side at least once on lengths that are too long, so that when you do it for real you stand a better chance of getting it right. I would also do this side first, because if you mess up you have one more chance of going to the next one. Albeit with a different clasp position. Clasp position is also something that may mean you end up buying a second strap if you are unhappy with the first go. It’s not like a bracelet where you can size first, then move clasp position. I do not mean any of this to sound negative (apart from poor tolerance on safety clasp side which could be designed out), it’s a lovely strap/clasp for the money, and not the end of the world if it goes wrong as you can buy half a side on its own. More expensive ones like Sinn are actually scary to cut!

In reality, the strap joining the safety clasp side of the clasp needs to be cut perfectly first time. You have to cut fairly close to it for it to fit, if not you will have to cut it a second time which is often harder. There is too little margin for error IMO. These are one of those things you do properly the second time.

Lug to lug 40mm? That looks like a Seiko SKX to me, which is definitely not 40mm lug to lug, more like 45/46mm