Idex Flangeless Nuts: Compatible with 1/4-28, PEEK, For Use With: For 0.18 in. O.D. Tubing, Port Style: 0.5 to 20 flat bottom, Flangeless nut, Quantity: Each, Certifications/Compliance: ROHS, Natural, Dimensions: 0.88 x 0.37 in. (2.23 x 9.4 cm), Length: 0.88 in., 2.23 cm