I bought a Glowbee and it worked fine for a couple years.I went to gas and couldnt get consistent Rpm readings from behind,front,left side of prop,right side,ect..One time i had a 21cc echo pushing a 16x8 MAS at 12,00 plus.I accidently left it outside after i got pissed when i was getting these fanominal readings[it rained that night].I bought the TNC tach from Dons and i can stand with my legs against the stab and take accurate readings now from 3 feet away.{Behind the engine].Close to $100.00 with shipping but it works great.