Nikon Extension Tubes.
PK-13 (2) one is older same distance not marked PK-13 (from pre 1970 "f" era.) These are 27.5mm ext.
The PK-13 has a divot/dent in the barrel they are double-walled and it seemed to perform as if the flanges are still parallel (full disclosure) if it were junk, I'd toss it out without wasting anyone's time
And PK-12 this is 14mm extension.
$21 each mailed.
Or SET of 3 for $52 mailed. in the USA
PK-13 (2) one is older same distance not marked PK-13 (from pre 1970 "f" era.) These are 27.5mm ext.
The PK-13 has a divot/dent in the barrel they are double-walled and it seemed to perform as if the flanges are still parallel (full disclosure) if it were junk, I'd toss it out without wasting anyone's time
And PK-12 this is 14mm extension.
$21 each mailed.
Or SET of 3 for $52 mailed. in the USA