Are these any good in practice? Ive seen the middleburn ones which seem pricey, anyone have any experience of the Brand X ones at CRC?

Ta

Yes, made of cheese.

The anodised aluminium collar that threads into the crank arm stripped straight out first time.

Luckily, its even softer than crank arm aluminium, so no lasting damage caused. In fact I've seen harder primula.

I'll give those a miss then. Which extracting bolts are the ones to go for then?

I've had the same problems with the Middleburn ones and even pricier TA originals. IME, they are for emergency use when out on tour. Back at base, I use a propa extractor.

I've never had a problem with the std shimano self extractors that have come with each of my road chainsets. There may be some flaoting about on CRC or Madison could send you some.

On MTBs I've stuck with normal crank bolts, as I have an extractor in the tool box. TBH I got them cos they were ano red and I was being a tart.

Hmmmm…..maybe i should move into the 21st century and get an external BB set up…. 😕
The only thing that puts me off with square taper is how easy it is to strip the thread in the crank arm when using the extractor tool

It is easy but only if you're a bit careless/ham fisted (or the crank has been on for ever and it's welded itself in place).

My self extractors are put to most use on my tandems. They (obviously) deal with twice the normal torque and load as an MTB/single. I strip and fettle regularly and despite this, sometimes have trouble self extracting without the ally retainer doming/splitting. For this reason, I only use them in anger when touring and therefore not carrying a pukka extractor tool.

At base, I exercise a bit of caution and use the standard tool and have had no stripping problems when using the tool with care. YMMV.