Use will eventually destroy the "gray" rubber cap which covers and protects the read switch (used on  models- 301, 361, 310, 309, 339, 369, 329, 1009, 319, 320). 

Read switch cap replacement kits are available through our web store www.xrite.com or by calling 800-248-9748. 

Just ask for part number 361-100-KIT unless you have a 301 which uses Part number 301-100-KIT. 

Installation instructions are included with the kit.