diff --git a/lago_data_model/reader.py b/lago_data_model/reader.py
index 6a9e97a..870eb0c 100644
--- a/lago_data_model/reader.py
+++ b/lago_data_model/reader.py
@@ -1,10 +1,11 @@
+import os
 import pyarrow as pa
 import pyarrow.parquet as pq
 from tqdm import tqdm
 from datetime import datetime
 
 class LagFileReader:
-    def __init__(self, file_path, chunk_size=1000):
+    def __init__(self, file_path, chunk_size=5000):
         self.file_path = file_path
         self.chunk_size = chunk_size
 
@@ -28,6 +29,8 @@ def _parse_stream(self):
                 yield {'TBP': current_tbp, 'readings': current_readings}
 
     def save_as_parquet_streaming(self, output_folder=".", prefix="instrument_readings"):
+        # Create the output dir if it doesn't exist
+        os.makedirs(output_folder, exist_ok=True)
         timestamp = datetime.now().strftime("%Y%m%d%H%M")
         output_path = f"{output_folder}/{prefix}__{timestamp}.parquet"
         
@@ -37,25 +40,28 @@ def save_as_parquet_streaming(self, output_folder=".", prefix="instrument_readin
         ])
         
         writer = None
-        chunk_data = []
+        tbp_values = []
+        readings_values = []
         
         try:
             for record in self._parse_stream():
-                chunk_data.append(record)
+                tbp_values.append(record['TBP'])
+                readings_values.append(record['readings'])
                 
-                if len(chunk_data) >= self.chunk_size:
-                    table = pa.table(chunk_data, schema=schema)
+                if len(tbp_values) >= self.chunk_size:
+                    table = pa.table([tbp_values, readings_values], schema=schema)
                     
                     if writer is None:
                         # TODO: Do we want to use snappy here? gzip seems like a better fit
                         writer = pq.ParquetWriter(output_path, schema, compression='snappy')
                     
                     writer.write_table(table)
-                    chunk_data = []
+                    tbp_values = []
+                    readings_values = []
             
             # Write remaining data
-            if chunk_data:
-                table = pa.table(chunk_data, schema=schema)
+            if tbp_values:
+                table = pa.table([tbp_values, readings_values], schema=schema)
                 if writer is None:
                     writer = pq.ParquetWriter(output_path, schema, compression='snappy')
                 writer.write_table(table)