On the left is a A2 70. What is the smaller one on the right?

Are they measured by head width and thread length?
If so could it be an A3 50(mm)

A2-70 isn’t the size, it’s the grading- A2 stainless, 700n/m tensile strength.

At a guess the one on teh left is an M6 (6mm wide thread) and the one on the right is an M5 but can’t tell from the pic. What are they from?

Important- countersunk bolt lengths include the head, which is unusual and confuses people. Normally to measure the length, it’s the shank only not the head. Guess how I found that out!

A2 is the grade of stainless steel. Being a countersunk screw the size is measured as the outside diameter of the threaded section by the overall length.

Edit, too late

Can you show a pic of a ruler as well? Scale is important!

You should have put them in front of a London bus or something for scale.

Edit – yeah, or a ruler… ^^^

I really need to find one the same size as the one on the right (i think) for my mech hanger. Currently it’s being held in place by the qr only and makes taking the rear wheel out a bit of a faff.

Oh! Mech hanger bolt might be very small indeed. What bike? and what is the one on the left from?

Measuring the thread of bolts is very easy to get wrong, do you own a set of calipers by any chance? Or, maybe one of those adjustable spanners with a scale on it?

have a look on here – the guy seems to have a shitload of stock and talks a good game regarding how comprehensive his catalogue is

(If you have a vernier gauge, it’ll give you the dimensions to compare with as well)

Yes it’s for a rear derailleur hanger for my Santa Cruz Stigmata.

I ordered the new hanger (over a year ago) from the distributor but I pretty sure they sent me the wrong one as although the hangers themselves are very similar the new one came with a much larger bolt (M5?)
When fitted (with the smaller bolt) there is some play (1-2mm)between the frame and new hanger.

2009 Norco Fluid LT here, just a little bump to see if anyone else can help 🙂

I’m sure the guys at BETD could help :

BETD

but I bet it’s M4 x 8 mm

So the the upshot is. Santa Cruz bizzarrely do not make a M3 bolt version of the hanger (which came fitted to the frame) so my only option is get the frame tapped for M5 bolt so I can fit the new hanger securely!