What size Allen key head do I need for the paslode screw, it’s the part number - 904 0226. I’ve tried using multiple ones but non seem to fit.

Thank you for your email, the below key is listed for the IM350+; https://www.lsengineers.co.uk/5-32-hexwrench-for-paslode-spit-im200-hafte-nail-gun-stapler-401331.html