<https://www.skimojo.com/product/rod-blockers-mkiii/#product>
<http://schema.org/description>
"Spare/Replacement Part - Set of 4 adjustable rod blockers. These can be set to the appropriate length and pre-inserted before the Telescopic Rods to prevent them from \"collapsing\" during use."
<https://www.skimojo.com/product/rod-blockers-mkiii/>