Most ALL Fisher Space Pens use our PR Refill. SPR and PR Refills are the same refill, the only difference is the packaging. The S means that the refill comes in a Blister Card, the cardboard backed, clear plastic holder like most things are in when you purchase them in a retail store.
If you need it to be shorter, just flex it back and forth at the break point and it will separate, leaving you the correct length refill. The PR and SU refills are NOT INTERCHANGEABLE!
Fisher Space Pens Fine Point Universal Carded Refill
WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov