This is a high-quality Archer replacement spur sprocket. This is a 7-tooth .325 pitch sprocket and it comes with a needle bearing.  The sprocket fits the following chainsaw models:  Husqvarna 340, 345, 346, 346XP, 350, 351, 353, 357, 450 Jonsered CS2141, CS2145, CS2149, CS2150, CS2152, CS2153, CS2156, CS2245 

Replaces OEM numbers 578097901 503873071, 503873072, 503873073, 503255201 and Oregon part# 108308X and Rotary part number 36-10819