<https://roballendiving.com/product/vecta-mechanism-w-loading-butt/#product>
<http://schema.org/description>
"Add a loading butt to your Rob Allen speargun.\r\n\r\nThe Complete Butt comes with a new trigger mechanism.  To install all you need to do is remove the existing mechanism and insert the new Complete Butt.\r\n\r\nThe Blank Butt is just the cartridge.  You will have to transfer all the internal parts when installing the butt on to the speargun."
<https://roballendiving.com/product/vecta-mechanism-w-loading-butt/>