Piston Pin Bushing for David Brown 1200 995 1210 1290 1390 1294 996 AD4/55One New Aftermarket Replacement Piston Pin Bushing for David Brown Tractors This piston pin bushing (also called a small end bushing or wrist pin bushing) fits at the small end of the connecting rod in the David Brown AD4 55 four cylinder diesel engine. It provides a precision bearing surface between the connecting rod and the piston pin, and is a critical component in engine rebuilds and overhaul work. Sold individually order one bushing per cylinder