Primer Bulb, Walbro 188-12-1, For Use With Grainger Item Number 44X183, 44X143, 44Z097, 44X137, For Use With Mfr. Model Number SRM-280U, PAS-280, BRD-280, PB-755ST, WA, WT, WY, WYJ, WYK, WYL, WYP, WZ, Fits Brand Echo, Walbro, Includes Primer Bulb, For Use With Carburetors That Require A 3/4 in. OD x 9/16 in. HT Primer Bulb